The invention relates to a thinning machine comprising a chipper, a loading platform for the transport of chips, a transfer duct connecting the chipper with the loading platform and transferring the chips from the chipper onto the loading platform, a boom for transferring timber to be chipped into the chipper and a tractor means for moving the machine. Conventional methods for thinning young forest utilize two different machines. A feller-harvester fells and debranches trees and cuts them into trunks of a predetermined length. The trunks are then gathered to the side of a strip road, wherefrom a separate forwarder collects them into its transport space and transports them from the forest to the roadside. A timber truck fetches the stacked trunks and transports them to the mill. The timber is then debarked and chipped. The amount of timber is measured by the measuring device of the harvester or in the roadside stacks. Even though the measuring accuracy of the measuring device of the harvester is reasonably high, the measuring device is an expensive investment and liable to damage in hard working conditions. Due to the increased forest utilization require¬ ments, the debranching of trees is often left undone, and the branches are chipped with the trunk. However, undebranched trees require much more transport space than debranched trees, and so the forwarder has to be driven to the thinning area a far greater number of times to transport the felled trees with their branches to the roadside. The assessment of the amount of timber is thereby based on mere estimations.

The feller-harvester and the forwarder moving through the forest damage tree roots and break the

surface of the ground and leave behind tracks collect¬ ing water that rots adjacent tree roots. Especially the forwarder, which has to move around in the stand and back and forth between the roadside and the stand, 5 cause great damage in the forest. In winter the hard frozen ground resists the strain caused by the heavy machinery. Trees felled by the feller-harvester and possibly debranched have to be gathered immediately after felling and transported to the roadside as they

10 will otherwise be covered with snow. It is also to be noted that two persons are required for thinning a stand, one for driving the feller-harvester and the other for driving the forwarder. Moreover, the feller- harvester and the forwarder are poorly compatible as

15. the work capacity of the feller-harvester is about 30 to 60 m ³ per work shift and that of the forwarder about 60 to 100 m ³ per work shift. The forwarder thus has to wait for long periods of time, which reduces the efficiency significantly. It is also difficult to

20 separate trunks from the logging waste by the forward¬ er, which makes the loading difficult and damage is frequently caused to growing trees by the forwarder boom when lifting the trunks. The transport of un¬ debranched trunks over long distances is very un-

25 economical as the weight/productivity ratio remains very low. It is also important to note that un¬ debranched trunks require a special transportation vehicle in which the trunks are placed in loading platforms provided with continuous side boards.

30 The object of the present invention is to provide a machine which reduces strains imposed on the forest during thinning, and allows a greater propor¬ tion of timber to be recovered and utilized. The invention is characterized in that the machine com-

35 prises a separate carrier detachable from and attach-

able to the tractor means, and fastening means for detaching and attaching the carrier; that the boom is provided with a felling unit for felling trees; that the chipper and the boom with the felling unit are mounted on said carrier so as to form a chipping unit separate from the carrier.

An essential idea of the present invention is that a single machine performs both the felling of trees and the transport of the trees to the roadside. Another essential idea of the invention is that the timber is chipped immediately after felling and the chips are passed into a container provided in con¬ nection with the tractor means. A further essential idea is that the chipping unit, which further com- prises a boom with a felling unit, can be detached from and attached to the tractor means and at the same time a chip transfer duct can be connected to the load space very easily. A major advantage of the invention is that a single machine is needed in place of two machines, which reduces considerably the labour costs and investments in machines and equipments. Further¬ more, the timber can be chipped at the felling place, and all possible timber can be recovered from the felled trunks. The amount of timber is easier to assess by measuring the volume or weight of the chips; at the mill in particular the amount of received chips is easy to measure. The chipping unit with the boom can be removed before the chips are transported from the forest to the roadside, where the transport plat- form is positioned, which makes it considerably easier for the machine to move through the forest. Finally, damage to the trees is reduced as a single machine moves through the forest and the tracks in the ground will not be deep. The invention will be described in greater

detail with reference to the attached drawings, in which

Figure 1 shows a machine assembly according to the invention; Figure 2a is a side view of the fastening means; and

Figure 2b is a top view of the fastening means. Figure 1 shows a thinning machine 1 comprising a chipper 1, a loading platform 3 for the transport of chips, a duct 4 for transferring the chips from the chipper onto the loading platform, and a boom 5 to which a debarking or debranching unit can be attached in addition to a felling unit 6. The debarking and debranching units may also be attached to the chipper 2, in which case the boom 5 with the felling unit 6 will be light and easily movable. The figure further shows fastening means 7a and 7b interconnecting a tractor means 8 and a chipping unit 9 comprising the chipper 2, the boom 5 with felling unit 6, and a carrier. When the tractor means 8 and the chipping unit 9 are interconnected by the fastening means 7a and 7b, the hydraulic and electric lines between the tractor means 8 and the chipping unit 9, required for controlling the chipper 2 of the chipping unit 9, the boom 5 with the felling unit 6, and a boggie 10a will also be interconnected. The machine 1 is designed to move on wheels through the forest, each boggie 10a to 10c comprising four wheels. The boom 5 and the felling unit 6 connected to it are prior art technique which will not be described more closely herein. Their function is to fell trees and transfer the trunks to the chipper 2. The chipper comprises a coarse feed mat 11 and a spiked feed roller 12 the purpose of which is to press the trunk against the feed mat 11 and simul- taneously feed it into the chipper 2. The chipper 2

can be turned in a sideward direction with respect to the chipping unit 9, so that the direction of feed of the chipper 2 can be selected according to the direc¬ tion of the trunk to be handled. The fastening means 7a and 7b join the chip transfer duct 4 into a con¬ tinuous passage from the chipping unit 9 to the loading platform 3. The chips are passed from the chipper 2 into the chip transfer duct 4 and further therethrough onto the loading platform 3. The tractor means 8 generates the energy required by the machine by a combustion engine or the like, and it comprises controllers required for displacing and controlling the machine as well as controllers required for the chipping unit 9 and the loading platform 3. As, however, the tractor means 8 complies with the prior art, it will not be described more closely herein.

Figure 2a shows a fastening means assembly com¬ prising the fastening means 7a and 7b. The fastening means 7b is provided with fastening hooks 14a and 14b controlled by hydraulic cylinders 13a and 13b. The figure further shows locking pins 15a and 15b on the side of the fastening means 7a, and aligning pins 16a and 16b in the fastening means 7b. The fastening means 7a also comprises mutually jointed annular cylinders 17a and 17b, so-called cross-roll bearings which enable the chipping unit to be turned about the horizontal axis of the tractor means 8. Figure 2a further shows a hydraulic cylinder 18 having one end connected to the carrier of the chipping unit and the other end to a fork member 19. It is thereby possible to turn the fork member 19 with respect to the chipping unit 9 about an axis 20 shown in Figure 2b. The figure further shows the chip transfer duct 4 which joins the chipper 2 and the loading platform 3. The duct 4 is preferably made such that soft plate-

like flanges are attached to the fastening means 7a and 7b in such a manner that when the fastening means 7a and 7b are interconnected, the flanges make the transfer duct 4 into a tight integral whole. Figure 2b is a top view of the fastening means assembly. The same references as in the above- described figures are used in Figure 2b. In the top view, a fastening hook 14c and a fastening pin 15c are also visible as well as cylinders 18 and 18' enabling the turning of the chipping unit 9 with respect to the axis 20. Figures 2a and 2b show by way of example connection pieces 21a and 21b for hydraulic and electric lines, and associated lines 22a and 22b.

The figures and the description related to them are only intended to illustrate the idea of the inven¬ tion. In its details, the machine according to the invention may vary within the scope of the claims. Accordingly, it may be preferable in certain cases that the transfer duct is completely separate from the machine body.