Field of the Invention

The present invention relates to an arrangement in a tree-processing assembly of the type comprising a frame which is connectible to the tip of a crane via a rotator and with which a pivotable carrier is hingedly connected, said carrier comprising at least one set of grapples for gripping and holding a log, and a cutting tool, such as a chain-saw guide bar, attached to a lower part of said carrier.

Such tree-processing assemblies can be divided into two different basic types, viz. so-called harvesters and pure felling assemblies. A one-grip type harvester com- prises, in addition to grapples and a cutting tool, a num¬ ber of limbing knives and at least one set of feed rolls by means of which the felled tree, which is held by the grapples, can be longitudinally fed relative to the car¬ rier and thus be freed from limbs. By means of such har- vesters, a tree can thus be felled, delimbed and cut to suitable lengths. In pure felling assemblies there are, however, no feed rolls, and therefore such assemblies can merely cut the tree at the root, without delimbing it. Background of the Invention In modern forestry, tree stands are in most cases thinned by means of precisely one-grip harvesters. A fre¬ quent problem in such thinning is caused by the thicket or shrub layer which is often to be found adjacent the trees which are to be thinned and cut. Thus, such thicket grows precisely around the lower part of the tree where this is to be cut, and thus prevents the clear view of the person who operates the harvester from a driving-cab at a con¬ siderable distance from the tree. Besides blocking the operator's view, the thicket causes trouble also by easily finding its way between the the trunk and the saw chain mounted on the guide bar of the harvester and serving as a cutting tool. As a result, the chain may slip or jam

and, consequently, lose its capacity of effectively cutting the trunk. To eliminate the problems caused by thicket surrounding the tree, one proceeds in practice usually by letting a special operator manually clean the tree stand from the shrub layer by means of a conventional bush saw, before the actual thinning is carried out. How¬ ever, this work is costly and, in turn, involves a number of drawbacks. One drawback is that the cleaning operator does not know in advance from which direction the harves- ter will be moved towards the tree which is to be thinned out, which means that he must remove all the thicket in a 360° sector around the tree. Removing in this manner sub¬ stantially all the thicket while leaving completely bare surfaces around the tree is, however, contrary to the most recent experience in environment protection, which recom¬ mends a certain amount of shrub layer in growing forest, thereby creating a favourable environment for forest ani¬ mals. By such clear-cleaning, the work of course also takes much time and thus is expensive. In practice, the cost for the manual thicket-cleaning only is estimated at 15-20% of the total thinning cost. A further problem is connected with the technical planning. Thus, especially for big forest owners with a great number of scattered stands it is extremely difficult to plan the cleaning ope- rator's work so as to be reliably coordinated with the thinning operation. Brief Description of the Inventive Idea

The present invention aims at obviating the above- mentioned drawbacks by eliminating the need for manual cleaning and creating opportunities for removing, as required, the obstructing thicket and shrub layer in immediate connection with the actual thinning operation. According to the invention, this is achieved in that on the lower part of the carrier of a tree-processing assembly of the type mentioned by way of introduction there is mounted a rotary saw blade which is pivotably movable between an inactive position and an active

position in which it can cut shrub layers and/or small trees.

According to a preferred embodiment of the invention, the saw blade is dismountably arranged on a shaft which is rotatably mounted and connected to a hydraulic motor which is arranged on a support member, such as a plate, which in turn is articulated to the lower part of the carrier, and a hydraulic cylinder extends between the support member and the carrier, the support member and, thus, the saw blade being pivotable by means of the hydraulic cylinder between a substantially vertical, swung-in position and a substantially horizontal, swung-out position. Brief Description of the Accompanying Drawings In the drawings FIG. 1 is a schematic, simplified front view of a one- grip type harvester with a cleaning arrangement according to the invention, FIG. 2 is a perspective view of the cleaning arrangement according to the invention, and FIGS 3 and 4 are enlarged side views of the cleaning arrangement according to Fig. 2 in two different positions. Detailed Description of a Preferred Embodiment of the Invention In Fig. 1, a one-grip type harvester is generally designated 1. The harvester comprises in per se known man¬ ner a frame 2 which via a rotator 3 is connected to a mounting 4 which in turn can be attached to the tip of a crane mounted on an off-road vehicle. The frame 2 is via a hinge (not shown) connected to a carrier which in its entirety is designated 5 and which in Fig. 1 is shown to be hanging in a substantially vertical position. By means of a hydraulic cylinder (not shown) acting between the frame 2 and the carrier 5, the carrier can be pivoted from the shown, vertical position to a substantially horizontal position in which the carrier is swung forwards in the plane of the drawing. The carrier 5 supports a number of

grapples 6, 6' , 6" which are each pivotable by means of a respective hydraulic cylinder 7 and each have limbing knives 8 in the form of obliquely ground surfaces forming cutting edges by means of which a passing log can be freed from limbs. Further the carrier 5 supports two feed rolls 9, 9' which are pivotable towards and away from each other. The feed rolls which are rotatable by means of built-in hydraulic motors 10, 10' serve to be pressed against a cut log received by the grapples and move the log axially relative to the carrier for delimbing thereof. In a lower, box-shaped part 11 of the carrier 5 there is a arranged a cutting tool in the form of a chain-saw guide bar 12 whose chain can be moved by means of a hydraulic motor 13, the guide bar itself being pivotable between an inactive position in the box-shaped part 11 and an active position swung out from the box.

As described so far, the shown arrangement is known in every essential respect.

According to the invention, a cleaning arrangement which in its entirety is designated 14 is connected to the lower part 11 of the harvester 1 or, more precisely, to the carrier 5. The characteristic features of this clean¬ ing arrangement are shown in more detail in Figs 2-4 to which reference is now made. The actively operating component in the arrangement 14 is a rotatable, toothed saw blade 15 which preferably is a standard-type blade and is dismountably arranged on a shaft which can be the output shaft of a hydraulic motor 17 which is mounted on a supporting plate 18. This is in turn articulated to the lower part of the carrier via hinges 19 arranged at the outer end of brackets 20 extend¬ ing from the lower part 11. To the upper side of the sup¬ porting plate 18 there is attached a mounting 21 for a hinge 22 of a hydraulic cylinder 23 whose opposite end is articulated to the carrier 5 via a hinge 24. In the embo¬ diment shown, the piston rod of the hydraulic cylinder is connected to the hinge 22, while the cylinder itself is

connected to the hinge 24 associated with the carrier 5. The dismountable arrangement of the saw blade 15 on the shaft 16 can advantageously be realised by means of two supporting discs 25 having internally threaded holes and screwed to an externally threaded portion of the shaft 16. A worn-out saw blade may thus be easily and quickly remov¬ ed from the shaft by unscrewing the outer supporting disc and be replaced by a new saw blade.

The supporting plate 18 is via an inner cross-member 26 connected with a base plate 27 which is spaced from the supporting plate, the inner half of the saw blade being accommodated in the space formed between the plates 18 and 27. As a result, the saw blade is kept well protected in it inactive, swung-in position shown in Fig. 3. In the area below the saw blade there is further arranged a yoke 28 projecting from the lower edge of the lower part 11 of the carrier. As is evident from Fig. 3, the yoke 28 pro¬ jects a distance beyond the base plate 27 of the saw blade holder so that the saw blade and its holder, in the inac- tive position illustrated, are reliably protected against mechanical damage caused by hard objects, such as stones, stumps and thick trees. Also in the active position illu¬ strated in Fig. 4, the yoke 28 protects the saw blade holder from mechanical damage in that the outer end of the yoke is positioned approximately in the same vertical plane as the outer parts of the saw blade holder, beyond which plane only a portion of the saw blade projects.

Although the yoke 28 is shown to be inclined in the drawings, it may also be designed to be entirely straight, extending from the bottom side of the lower part 11. Such a design would also allow the same blade to be slightly lowered, more precisely by arranging the brackets 20 lower down on the outside of the lower part 11.

As shown in Fig. 2, the hydraulic cylinder 23 is double-acting and fitted with suitable hydraulic lines 29, 29' . Analogously, the hydraulic motor 17 is supplied with hydraulic fluid via lines 30, 30'. It is per se conceiv-

able to control the hydraulic motor 17 and the hydraulic cylinder 23 separately by rotating the saw blade indepen¬ dently of whether the hydraulic cylinder is activated or not. In practice, it is however preferred to synchronise the operation of the hydraulic motor with the operation of the hydraulic cylinder, more precisely in such a manner that the starting of the saw blade 15 is automatically accompanied by activation of the positive chamber of the hydraulic cylinder, i.e. the saw blade is swung out a while after it has been caused to rotate. Inversely, the saw blade can be swung back to its inactive position a while after it has been caused to stop. Such synchronisa¬ tion can be carried out by suitably integrating the above- mentioned lines into the existing system of hydraulic lines that is required for the other components of the harvester.

The above-described arrangement operates as follows. When the harvester 1 should be moved against the selected tree which is to be cut and is surrounded by a shrub layer blocking the operator's view, the saw blade 15 is swung out to the active position shown in Fig. 1. In this state, the saw blade can be quickly moved forwards to individual shrubs and small trees by moving the tip of the crane and rotating the entire harvester via the rotator 3, the shrubs and small trees being cut as soon as the rotating saw blade comes into contact with them. It is of course sufficient to remove merely the vegetation in a limited sector (e.g. 90-120°) in the area in front of the tree which is to be thinned, whereas the remaining vegetation surrounding the tree may be left. Such cleaning can in practice be carried out very quickly, for example in 10-20 s. After the thinning operation has been finished, the saw blade is stopped and swung in to the position shown in Fig. 3, whereupon the harvester, without being obstructed, can smoothly and effectively be caused to grasp the tree and process it in the usual manner, i.e. fell, delimb and cut it to suitable lengths.

The advantages of the invention are obvious. Accord¬ ing to the invention, any need for costly manual cleaning thus is eliminated, which means, inter alia, that the planning of the thinning operation is facilitated to a considerable extent. Moreover, there is no need for com¬ pletely cleaning the area surrounding a tree which is to be thinned in that the direction of travel of the har¬ vester towards the tree is already determined when the cleaning arrangement according to the invention is acti- vated. This means that only a limited sector in front of the tree need be cleaned. Possible Modifications of the Invention

The invention is of course not restricted merely to the embodiment described above and shown in the drawings. Thus, the saw blade included in the arrangement can be mounted in other types of holder than precisely the one illustrated in the drawings, and the saw blade can be swung between its two positions in some other way than by means of a hydraulic cylinder, although in practice pre- cisely a hydraulic cylinder is preferred. Furthermore, the cleaning saw blade can be mounted on an arm which is pivotable relative to the carrier in a horizontal plane instead of in a vertical plane, and then, more precisely, between an active front position and an inactive rear position, instead of a swung-out and a swung-in position as illustrated in the drawings. It is also possible to apply the invention also to other types of tree-processing assemblies than precisely a one-grip type harvester. Con¬ sequently, the invention may also be applied to pure fell- ing assemblies and two-grip type harvesters.