The present invention relates to a barking tool for barking machines of the type having a rotation ring which is rotatable about an axis of rotation and which carries a plurality of barking tools, comprising a swinging arm which, at a free front end, has a processing means with a cutting edge substantially parallel to said axis of rota¬ tion and which, at an opposite rear end, is fixable to a tool shaft associated with the rotation ring and rotatable in relation thereto, the cutting edge of said processing means being resiliently applicable, by rotation of said tool shaft, against the circumferential surface of an unbarked log of wood, said arm having a front facing the feeding direction of the logs fed to the machine and form¬ ed with a climb-up edge, as well as a back opposite to said front. Description of the Prior Art

Barking machines of this type are available in seve- ral different designs which all include a rotation ring formed with a central hole through which the logs are fed in their longitudinal direction during the barking pro¬ cess. A number of barking tools, usually five, are pro¬ vided on the circumference of the rotation ring. The bark- ing tools are in the form of swinging arms which are pivotable in a plane substantially perpendicular to the feeding direction of the logs and which are spring-loaded so as to be resiliently applicable against the circumfe¬ rential surface of the logs, adapting themselves to the irregularities thereof. Since the rotation ring rotates while the logs are fed in their longitudinal direction, the bark will be peeled off in long, helical strips. Since the swinging arms are arranged on that side of the rota¬ tion ring which faces the feeding direction of the logs, the peeled-off bark strips will move towards the rotation ring, owing to the direction of movement of the logs, and may in unfavourable circumstances cause stoppage by get-

ting tangled up in the tool shafts, or block the rotation ring. It goes without saying that this is highly incon¬ venient, since the operator supervising the barking then has to stop the machine and remove the bark strips by hand. This inconvenience is especially pronounced during the period of sap flow or when barking trees with long- fibre bark. In theory, this inconvenience might be obviat¬ ed by arranging the barking tools on the back of the rota¬ tion ring, i.e. the side facing away from the incoming logs. However, such a construction involves certain disad¬ vantages, since the distance between the feeding rollers required for the longitudinal feeding and provided before the rotation ring and the barking tool, becomes too long, which considerably increases the risk of breaking and a poor barking result owing to curved logs. Summary of the Invention

The present invention aims at obviating the above inconveniences and providing a barking tool which removes the bark from the machine in the area before the rotation ring without any risk of the ring stopping. This and other aims of the invention are achieved by a barking tool which is characterised in that the arm, at least in the area of its free end, has a first portion which faces the feeding direction and is formed adjacent to the climb-up edge and which has at least a certain axial extension relative to the axis of rotation, as well as a second portion which extends from said first portion and has a pronounced extension radially inwards to the axis of rotation from said first portion and which is situated further down- stream, as seen in the feeding direction, than said first portion, said first portion extending in the longitudinal direction of the arm substantially from that end of the processing means which is located closest to the front of the arm, while said second portion extends in the longitu- dinal direction of the arm substantially from that end of the processing means which is located closest to the back of the arm, which means that said two portions cooperate

in order to guide the bark in a substantially perpendi¬ cular direction out and away from the axis of rotation. Further Elucidation of the Prior Art

SE 430,391, for instance, discloses a barking tool of the type mentioned in the introduction to this specifica¬ tion. Since the cutting edges of the barking tools in an initial position are brought close together by the spring load in an area immediately adjacent to the extension of the axis of rotation of the rotation ring, each barking tool has to be formed with a so-called climb-up edge. This enables the tool to pivot aside and climb to place the cutting edge on the circumferential surface of an incoming log when the log end hits the barking tools. As a rule, the climb-up edge has previously been located on the bark- ing-tool edge closest to the log and the centre of rota¬ tion, as illustrated at 5 in Fig. 1 of SE 430,391. Since the climb-up edge also has to be located on that part of the barking tool which faces the feeding direction and which is first hit by an incoming log, the climb-up edge has helped to guide the bark inwards to the rotation ring, thus preventing it from leaving the machine in the area before the rotation ring. Fig. 9 of SE 430,391 illustrates another embodiment of a barking tool in which the swinging arm has been given a substantially U-shaped cross-section with two flanges to reduce the weight and stiffen the con¬ struction. The flanges are arranged to face the feeding direction of the logs to enable the flange closest to the circumferential surface of the log to serve as a climb-up edge. As above, this climb-up edge will prevent the bark from leaving the machine in the area before the rotation ring.

US 2,911,020 discloses a barking tool for rotation- ring barking machines, which has been designed to remove the bark from the rotation ring. To this end, the arm of the tool has been equipped with a rather large, arcuate wing which extends from the arm proper, both in the for¬ ward direction contrary to the feeding direction and in a

direction away from the axis of rotation of the rotation ring. However, the'chances that this prior-art barking tool succeeds in guiding the bark as intended must be regarded as slight, there being no means provided behind the processing edge to intercept the bark and guide it in the desired direction. As appears from the cross-section in Fig. 8 of US 2,911,020, the bark-guiding inside of the wing merges, at an angle exceeding 180°, with a flat por¬ tion extending substantially parallel to the axis of rota- tion. Thus, there is an obvious risk that the bark will follow the flat inside of the tool for a certain distance, to be then guided into the rotation ring. Another drawback of this prior-art tool is that the shape of the wing ren¬ ders it unsuitable as a climb-up edge. The cross-section of the wing is simply too long and too thin, and the wing is therefore liable to be broken by incoming logs. Brief Description of the Drawings

In the drawings, FIG. 1 is a perspective view of a barking tool according to the invention,

FIG. 2 is a side view of the barking tool as seen in a direction parallel to the feeding direction of the logs, FIG. 3 is a side view of the barking tool as seen per- pendicular to the feeding direction of the logs,

Fig. 4 is a side view of the barking tool as seen from an angle perpendicular to the view of Fig. 3, FIG. 5 shows cross-sections of the barking tool taken according to the indications in Fig. 2, and FIG. 6 is a side view of the barking tool in operation. Description of the Preferred Embodiment

The drawings illustrate a barking tool 1 according to the invention. In the preferred embodiment, the barking tool comprises a swinging arm 2 and a processing means 3 in the form of a releasable cutting steel which is fixed to the swinging arm by a bolt 4. The cutting steel has a front edge 5, serving as processing edge, which extends

substantially parallel to the intended feeding direction of the logs. The rear end 6 of the barking tool is, by bolts 7, fixed to a holding member 10 which in turn is non-rotatably connected to a tool shaft 11. As indicated above, the present invention is applicable to a rotation- ring barking machine, which includes a plurality of bark¬ ing tools, preferably five, which are pivotably connected to a rotation ring (not shown) by the tool shafts 11. The rotation ring is formed with a central hole through which logs of wood are fed in their longitudinal direction while being barked, the axis of rotation of the rotation ring being parallel to the feeding direction of the logs. Also the tool shafts 11 are parallel with the feeding direc¬ tion, and the barking tool is thus able to pivot substan- tially perpendicular to the circumferential surfaces of the logs. The tool shafts, which are spring-loaded, strive to move the processing edges 5 of the barking tools con¬ trary to the axis of rotation of the rotation ring.

As shown in Figs 2 and 5, the swinging arm includes a first portion 8, a second portion or web 12, an inner flange 13 and an outer flange 14. By the word 'inner' is here meant closest to the axis of rotation of the rotation ring, and by the word 'outer' is meant furthest away from the axis of rotation of the rotation ring. The inner and outer flanges 13, 14 are situated on the back 30, i.e. on that side of the swinging arm which faces in the feeding direction of the logs. On the opposite front 31 of the swinging arm, i.e. that side which is first hit by an incoming log, the first portion 8 is formed with a climb- up edge 15. When a log hits the barking tool, the climb-up edge is to engage the end surface of the log, whereupon the barking tool will be raised on to the circumferential surface of the log owing to its rotation relative to the log. As appears from Fig. 5, an inner edge 17 of the second portion 12 is always located closer to the axis of rotation of the rotation ring than is the climb-up edge 15 in a corresponding cross-section.

Figs 2, 3 and 4 illustrate in more detail the con¬ struction of the processing means 3. As shown, the inner edge 17 has an extension edge 17' on the inner part of the processing means 3 facing the back, the extension edge 17' extending almost up to the processing edge 5, more pre¬ cisely that end 18 of the processing edge which faces in the feeding direction of the logs. The edge 17' is arrang¬ ed on a wedge-shaped bead 19 provided on the processing means. Further, the climb-up edge 15 extends from, and on a level with, the end 20 of the processing edge facing the feeding direction of the logs. The edge 15' of the pro¬ cessing means facing the feeding direction forms an exten¬ sion of the climb-up edge. As seen in a plane perpendicu¬ lar to the axis of rotation, the climb-up edge 15 extends rearwards from the processing edge 5, while gradually increasing its distance from the inner edge 17, and has a slightly curved shape up to a point 21 where it turns so as to be on a level with the outer flange 14.

In Fig. 6, an arrow 22 indicates the direction of rotation of the rotation ring and the barking tool. The reference number 23 designates a log of wood which still carries its bark 24. When the barking tool is rotated, the bark will be peeled off in long strips 25 which, by the bead 19 and a bark-guiding groove-shaped surface 16 formed by the first and second portions 8 and 12, will be removed in a substantially perpendicular direction away from the axis of rotation of the rotation ring. Owing to the cen¬ trifugal force, the bark strips will be thrown out of the machine, approximately at the point 21, and will therefore not be drawn into the rotation ring. As appears most clearly from Fig. 3, the swinging arm 2 is slightly bent outwards contrary to the feeding direction at a point 26 and is slightly bent inwards in the feeding direction on a level with the point 21. This arrangement is meant to facilitate the removal of bark from the tool, since the front tool end with the barking edge will, in its entire¬ ty, rotate ahead of a plane which is perpendicular to the

axis of rotation and is located ahead of the longitudinal extension of the tool shaft. Thus, the bark will be thrown out and away from the machine without any risk that it hits the holding member 10 or the rear end 6 of the tool. As appears from Fig. 5, the bark-guiding surface of the second portion 12 is inclined relative to the vertical plane. This surface might also be vertically aligned, i.e. arranged in a plane perpendicular to the axis of rotation, but tests have shown that the swinging arm is advanta- geously designed in accordance with the preferred embodi¬ ment illustrated. The bark-guiding surface of the second portion 12 in the section I-I, which is taken immediately behind the cutting steel 3, forms an angle of about 45° with the vertical plane. The bark-guiding surface of the second portion is then gradually turned and forms in the section V-V, i.e. at the point 21 where the bark is nor¬ mally thrown out and away from the tool, an angle of about 23° with the vertical plane. Since the transversal exten¬ sion of the bark strips when peeled off normally forms an angle of 90° with the vertical plane, such a design of the bark-guiding portion will cause the bark to gradually turn. Preferably, the bark-guiding surface of the second portion 12 may form an angle of 20-50° with the vertical plane. The inner surface of the first portion 8 also forms part of the bark-guiding surface in that it prevents removal of the bark caused by the centrifugal force in the vicinity of the barking processing edge. Should the bark be thrown out in the area before the point 21, the first portion 8 moves it a distance contrary to the feeding direction. Fig. 5 shows a flange 28 which forms an exten¬ sion of the climb-up edge 15. However, the flange 28 does not have a climbing-up or bark-guiding function since it is situated between the point 21 and the rear end 6 of the swinging arm. Thus, the flange 28 only serves to reinforce the swinging arm. In practice, the length of the bark- guiding surface 16 should be at least a third of the entire length of the swinging arm.

As appears from Fig. 4, the bark-guiding surface of the second portion 12 extends, as seen in a plane parallel to the axis of rotation, from a position close to the end of the processing edge facing the back and a distance con- trary to the feeding direction of the logs up to a point 29 where the second portion 12 turns towards the longitu¬ dinal extension of the swinging arm. This design has seve¬ ral advantages. Thus, the processing edge 5 can be compa¬ ratively long, and at the same as the swinging arm can taper a distance behind the processing edge to be more light. Further, the bark will be broken contrary to the feeding direction immediately after having been peeled off, and is thus broken in rather short pieces, which is especially advantageous in the barking of logs with long- fibre bark. Finally, the bark is guided contrary to the feeding direction, which facilitates the removal away from the tool.

The embodiment of the barking tool described above and illustrated in the drawings may be modified in many ways within the scope of the appended claims. Thus, the barking tool need not have a releasable processing means, but the cutting edge may be integrally formed with the swinging arm. Also, fixing on the tool shaft can be per¬ formed in different ways, e.g. by welding. Further, the bark-guiding surface 16 may be designed in many different ways. Thus, this surface need not be composed of two sub¬ stantially flat surfaces at an angle to one another, but it may have a continuous alteration of the angle, e.g. have an arcuate shape. The essential thing is that the flat surfaces or the tangents of the arcuate surface at the inner edge 17 and the climb-up edge 15, respectively, form with one another an angle of less than 180°, suit¬ ably 90-160°, preferably 110-140°. Naturally, the process¬ ing means need not be provided with a bark-guiding bead 19, but the bark may be guided entirely by the bark-guid¬ ing surface 16 on the swinging arm.