WO1993019909A1

WO1993019909A1 - Harvester unit

Info

Publication number: WO1993019909A1
Application number: PCT/FI1993/000143
Authority: WO
Inventors: Pentti Lastunen
Original assignee: Lastusen Konepaja Oy
Priority date: 1992-04-07
Filing date: 1993-04-06
Publication date: 1993-10-14
Also published as: FI91588B; FI921536A0; FI921536A; AU3892093A; FI91588C

Abstract

The object of the invention is a tree harvesting unit comprising a frame part (1), a fixed feed roller (2), or similar, incorporated in the frame part, and feed rollers (3, 4), or similar, movable outwards or inwards in relation to the fixed feed roller for moving a tree trunk (5) longitudinally (P) between and by means of the feed rollers as the feed rollers are rotated, and the means necessary for processing trees. The frame part (1) comprises two mutually connected branch members (6, 7) of appropriate length constituting a directionally rigid frame construction and protruding from the area of the fixed feed roller (2), thereby forming with one another an acute angle (K). Both of the branch members include at leat one slide (8, 9) which is movable, principally in the direction of protrusion (D1, D2) of the corresponding branch member, or in the direction opposite to this. The said movable feed roller (3, 4), or movable feed rollers, is secured to the slide (8, 9) provided in each branch member, on the sides facing one another.

Description

HARVESTER UNIT.

The invention relates to a tree harvesting unit comprising a frame part, a fixed feed roller, or similar, incorporated in the frame part, feed rollers, or similar, movable outwards or inwards in relation to the said fixed feed roller for moving a tree trunk longitudinally between and by means of the feed rollers as the feed rollers are rotated, and the means necessary for processing trees.

In known tree harvesters, the frame part incorporates one or two fixed feed rollers, or a corresponding belt or chain feed. Incorporated in the frame part, at the fixed feed roller, is a bar extending transversely in relation to the tree trunk, the ends of the bar being connected, by means of joints, to swinging arms and movable feed rollers provided at the ends thereof. Typically, the length of the swinging arms of the movable feed rollers is in the order of half the length of the transverse bar, and the arms are usually swung towards or away from the fixed feed roller by hydraulic mechanisms. With the joints axially approximately parallel to the tree trunk, the movable feed rollers are capable of pressing against tree trunks of different diameters by turning, upon the action of the hydraulic actuating mechanisms, towards the fixed feed roller. When the tree trunks to be handled are neither very large nor very small, the arrangement described above works satisfactorily. If very large tree trunks, in other words, tree trunks exceeding 50 cm in diameter, are to be handled, using the construction described above presents difficulties. More specifically, both the length of the transverse bar and the length of the swinging arms must then be increased considerably, thereby making the apparatus so large in width and so heavy in weight that, for example, bringing it into contact with the desired tree trunk between other trees is in many instances rendered impossible. Further, due to the leverage effect produced by the arms, increasing the length of the arms involves a considerable increase in the amount of force required, as a consequence of which the size of the apparatus must be further increased. Therefore, up to the present time it has not been possible to construct a practical harvester for processing tree trunks more than approximately 50 cm in diameter. With very small tree trunks there is a risk of the movable feed rollers coming into contact with one another or with the fixed feed roller,, wherefore the processing of a tree trunk must be discontinued at an insufficient trunk diameter. This phenomenon is especially common in harvesters generally dimensioned and designed with a view to trunks with as large a diameter as possible. If, on the other hand, the dimensioning is done with a view to processing tree trunks of small diameters, these outer dimensions involve a loss in maximum trunk diameter.

Another known alternative for the construction of tree harvesting units is to arrange the axis of rotation of the fixed feed roller or fixed feed rollers and the axis of rotation of the feed roller or feed rollers movable relative to the fixed feed roller so that they are approximately parallel to each other, in which arrangement the movable feed rollers are moved in a direction approximately perpendicular to the said axes of rotation. A construction of this type enables the handling of very small tree trunks but presents the same difficulties with large tree trunks as the apparatus described above, because the width of the apparatus consists in the sum of the desired maximum diameter of tree trunks and the diameters of the feed rollers positioned on both sides thereof.

Furthermore, the diameter of the feed rollers would have to be increased in proportion to the diameter of tree trunks so as to retain sufficient motive force.

It is therefore an aim of the present invention to provide a tree harvesting unit enabling the handling of very large tree trunks without being impractically large in its outer dimensions. More specifically, it is an aim of the invention to provide a tree harvesting unit with a maximum width only slightly greater than the maximum diameter of tree trunks to be handled. Further, is is an aim of the 5 present invention to provide a tree harvesting unit of the said type that may also be employed without difficulty for handling very small tree trunks. Further, it is an aim of the present invention to provide a tree harvesting unit of the said type that may be of a robust construction without 10 being exceedingly heavy in weight, and where the forces required for pressing the feed rollers against a tree remain reasonable. It is also an aim to provide a tree harvesting unit of the said type which is simple in construction and therefore inexpensive in price.

15 The disadvantages described above can be eliminated and the aims determined above can be met with a tree harvesting unit according to the present invention, as characterized in the characterizing part of claim 1.

The principal advantage provided by the present invention 20_. is considered to be that a tree harvesting unit according to the present invention is small in size as compared with the trees handled, light and robust. Another advantage provided by the invention is that the driving force required to press the feed rollers against a tree trunk 25 with sufficient force is roughly of equal magnitude to the compressive force irrespective of the diameter of the tree being handled, wherefore the driving mechanisms designed will not have to be oversized.

In the following, the invention will be described in detail 30 with reference to the accompanying drawings.

Fig. 1 is a view of a tree harvesting unit according to the invention crosswise in relation to the length of the tree trunk being handled as seen from direction I of Fig. 2. Fig. 2 is a side view of the harvesting unit in Fig. 1 as seen from direction II of Fig. 1.^'

Fig. 3 is a more detailed view of the feed roller arrangement according to the invention as shown in Fig. 2.

Fig. 4 is a longitudinal sectional view of the feed roller moving mechanism used in a harvesting unit according to the inventio .

Fig. 5 is a cross-sectional view of the moving mechanism in Fig. 4 along the plane A-A of Fig. 4.

Fig. 6 is a cross-sectional view of a second embodiment of the feed roller moving mechanism used in a harvesting unit according to the invention.

Fig. 7 shows a solution corresponding to that of Fig. 1 according to a second embodiment.

Fig. 8 shows a solution corresponding to that of Fig. 2 according to a second embodiment.

Fig. 9 shows a solution corresponding to that of Fig. 6 according to a second embodiment.

The tree harvesting unit according to the present invention comprises a frame part, generally indicated by reference number 1, and a fixed feed roller 2 joined to the said frame part, or, when required, several fixed feed rollers positioned in alignment, a belt or chain feed, or similar. The tree harvesting unit further comprises feed rollers 3 and 4 movable outwards or inwards in relation to the said fixed feed roller 2 for pressing a tree trunk between the rollers to move the tree trunk longitudinally P between and by means of the feed rollers as the feed rollers 2, 3, 4 are rotated about their axes of rotation 12, 13, 14. The number of movable feed rollers may also be greater than the two stated above, being, for example, four, or a belt or chain feed, or similar, may be used in their stead. Naturally, the tree harvesting unit includes the means necessary for processing trees, such as delimbing knives 40 and a cross-cut saw 41, but since they are typical as such they will not be discussed in detail in this application.

The frame part 1 comprises two mutually connected branch members 6 and 7, which together form an acute angle K. In the embodiment herein described the angle K between the branch members 6, 7 is approximately 60°, which, according to present knowledge, seems to be the most preferable value. It is essential that the said angle K be an acute angle, in other words, an angle of less than approximately 90°. Angle values greater than this result in considerable alterations in the dimensioning of the construction and cause problems similar to those found in prior art equipment. At its most acute, the angle K between the branch members may be approximately 30°, smaller angle values resulting in a considerable increase in the height of the unit. The angle range considered to be practicable in every respect is 50-70°. According to the invention, the construction is at least directionally rigid, in other words, the angle K described herein between the branch members is invariable in a finished apparatus.

In the embodiment shown in Figs. 1 and 2, the branch members 6 and 7 each consist of three parallel tubes 24a, 24b, 31a, and 25a, 25b, 31b, or corresponding profiles. These tubes or profiles are secured in a fixed position at their one end to a transverse base element 22 by, for example, welding. The result is a rigid frame construction consisting of the base element 22 and the branch members 6, 7 protruding from the base element at an angle K, thereby forming the said acute angle between the branch members away from the base element, and preferably in such a manner that the plane 11 of the said angle is perpendicular to the length of the base element. The frame part of the embodiment described is fully rigid, not merely directionally rigid in the aforementioned sense. During operation, a tree trunk 5 moves between the branch members 6 and 7, the longitudinal direction P of the tree trunk thus being in the main parallel to the length of the base element. Thus the tubes or profiles 24a, b and 31a of one branch member 6 are essentially parallel to one another, and similarly, the tubes or profiles 25a, 25b and 31b of the other branch member 7 are essentially parallel to one another, and the said branch members form an angle K between one another. The base element 22 further includes support means 23 on the side away from the branch members 6, 7 for attaching the entire tree harvesting unit to and mounting it for support on a machine not shown in the drawings. The branch members 6, 7 are of appropriate length so that the movable feed rollers 3, 4 movable along them may be positioned to press against tree trunks 5 of various diameters with a movement corresponding in range to the said length, in other words, the movable feed rollers may be brought closer to or moved away from the fixed feed roller along the branches. The length L of the branch members 6, 7, as measured from the point of contact between the fixed feed roller 2 and the tree trunk to the end of the branch member, must evidently be not less than the radius R, in other words, half the diameter, of the largest tree trunk to be handled.

The fixed feed roller 2 is located between the branch members 6, 7, adjacent to the base element 22, so that the plane of rotation 10 of the fixed feed roller bisects the aforementioned acute angle K. The harvesting unit is thus in the main symmetrical in relation to the plane of rotation 10 of the fixed feed roller 2. It is understood that certain "individual members and actuating mechanisms may cause variations from this. The fixed feed roller 2 is driven by a motor 38, preferably a hydraulic motor, and the line 12 indicating the axis of rotation of the motor and the feed roller is parallel to the plane 11 of the angle K. The first branch member incorporates at least one slide 8, and in the embodiment according to the Figs. herein described each of the aforementioned tubes incorporates a slide 8 of its own, and, correspondingly, the second branch member 7 incorporates at least one slide 9, or, as shown in the Figs. , each of the aforementioned tubes incorporates a slide 9 of its own, which slide or slides are movable, principally in the direction of protrusion Dl and D2, respectively, of each branch member, or in the directions opposite to these. Secured to the slide or slides 8 and 9, respectively, provided in each branch, on the sides facing one another, is a movable feed roller 3 and 4, respectively. The movable feed rollers 3 and 4 are preferably located between two adjacent tubes 24a and 24b, and 25a and 25b, respectively, and the distance between the tubes in the direction P is greater than the diameter of the feed roller, so as to allow the feed roller to turn in a manner to be described in more detail. The said feed rollers 3 and 4 are also driven by their own motors 39, preferably hydraulic motors, and the axial rotation lines 13 and 14 are also at least approximately parallel to the plane 11 of the angle K between the branch members. Thus all feed rollers 2, 3, 4 are capable of moving a tree as they rotate in the longitudinal direction P of the tree trunk. The branch members 6, 7 are preferably straight, and the slides 8, 9 move along them by, for example, sliding, whereupon the movable feed rollers 3 and 4 move along with the slides away from or closer to one another and the fixed feed roller 2. When the movable feed rollers 3 and 4 are close to the ends 26 and 27 of the branch members 6 and 7 their distance from one another and from the fixed feed roller is at its greatest, thus enabling the handling of a tree trunk of great radius R. When the slides are pulled closer to the fixed feed roller, the movable feed rollers 3, 4 secured to them move closer to both one another and to the fixed feed roller, thus allowing a tree trunk of smaller radius R to be handled. The movable feed rollers 3 and 4 are linked to the slides 8, 9 by means of joints which allow the feed rollers to be tilted in relation to the slides about the axial lines 16 and 17. These axial tilt lines 16, 17 are in the main perpendicular to the plane 11 of the angle K between the branch members, and are situated adjacent to the said feed rollers 3, 4 with respect to the axes of rotation 13, 14 of the said feed rollers. Preferably, the said axial tilt lines 16, 17 are as close to the feed rollers as possible with respect to the axes of rotation of the feed rollers. Most preferably, the said axial tilt lines 16, 17 are adjacent to each movable feed roller 3, 4, on the side facing the fixed feed roller 2. Thus the moment resisting the action of a force-applying means 15 causing the rollers to tilt remains small, and furthermore the distance of travel of the acting face of the roller is short, so that the roller assumes the correct position against a tree trunk 5 merely by tilting against it. The said movable feed rollers 3, 4 are loaded by the force-applying means 15 to tilt about their axial tilt lines 16, 17 in a direction of rotation S which between the branch members 6 and 7, in other words, within the area of the angle , is directed in the main towards the fixed feed roller 2. The said tilting of the movable feed rollers about the axial lines 16, 17 is limited, so that when the feed rollers are tilted in their extreme position by the force-applying means 15, the planes of rotation 18, 19 of the said feed rollers are approximately parallel to the directions of protrusion Dl and D2, respectively, of the respective branch members 6 and 7. With this arrangement, the movable feed rollers 3, 4 assume the correct position for a tree trunk of small diameter when they are closest to the fixed feed roller 2, as illustrated by dotted lines in the Figs. On the other hand, the capability of yielding flexibly against the loaded direction of rotation S enables the movable feed rollers 3, 4 to assume the correct position against a large tree trunk, the planes of rotation of the movable feed rollers thus becoming approximately parallel to the radius of the tree trunk, and the axial rotation lines 13 and 14 becoming approximately parallel to the tangent of the tree surface. This provides for maximum gripping force and feeding force of the feed rollers. This arrangement further allows a tree trunk of large diameter to advance between the branch members and the movable feed rollers 3, 4 at the ends 26, 27 of the branch members when a new, unprocessed tree trunk is first gripped. With the frame part 1 of the harvesting unit consisting of tubes or profiles spaced a certain distance from one another, as mentioned before, the required space is provided for the movable feed rollers to tilt. In this case, the feed rollers are partially coinciding with the branch members 6, 7, and the dimensions of the apparatus are the smallest possible.

According to the invention, both branch members 6, 7 incorporate at least one actuating mechanism 20, 21, and in the preferred embodiment shown in the Figs. each tube or profile incorporates such an actuating mechanism 20, 21 for moving the slides 8, 9 by force towards the fixed feed roller 2. The tree trunk 5 is pressed by a movement in the said direction between the feed rollers, and after the trunk has been processed the slides and the movable feed rollers secured to them are moved by means of the said actuating mechanisms 20, 21 back to the outer ends 26, 27 of the branch members, after which the harvesting unit is ready to grip a new, unprocessed tree trunk. This gripping of a tree trunk is effected by positioning the branch members 6, 7 with the feed rollers 3, 4 provided at the ends thereof on two sides of the tree trunk 5, whereafter the slides 8, 9 are moved by means of the actuating mechanisms 20, 21 in the directions opposite to the directions of protrusion Dl, D2 of their respective branch members, in other words, towards the fixed feed roller 2, whereupon the movable feed rollers are positioned against the tree trunk, and the tree trunk 5 is pressed between the fixed feed roller and the movable feed rollers. Thereafter, the processing of the tree trunk may be commenced in the manner known as such. Naturally, the movable feed rollers are provided with motors 39 for this purpose, preferably hydraulic motors, similarly to the fixed feed roller. As the movable feed rollers 3, 4 are, according to the invention, located very close to the arm members 6, 7, or even coinciding with them, at least partially, the distance between the actuating mechanism 20, 21 of the slides and the movable feed roller is short, and therefore the actuating mechanism acts on the feed rollers essentially at its full capacity. In other words, the leverage effect produced by the distance between the actuating mechanism and the feed roller is small, wherefore the actuating mechanism does not have work against a moment of resistance. This is accomplished due to the distance between each axis of tilt 16, 17 and the centre line of the respective arm member 6, 7, and especially between the said axis of tilt and the line of action of the said actuating mechanism 20, 21, being as short as possible, and, in addition, the distance between the axes of tilt 16, 17 and the feed roller being short. The axes of tilt 16, 17 may be located immediately adjacent to the branch members, as shown in the Figs., or coincide with them.

The apparatus according to the invention can be made more robust, especially to resist the torsion exerted by a tree trunk, by linking the slides 8, 9 in each branch member 6 and 7, to one another by means of a support bar 35 and 36, or similar, parallel to the base element. Consequently, these support bars 35 and 36 move as one piece with the respective slides 8 and 9. It is possible that the said bars 35 and 36 themselves are shaped to constitute slides. The aforesaid delimbing knives 40 and the cross-cut blade 41 with their associated actuating mechanisms are preferably attached to the said support bars 35 and 36. In particular, the outermost of the delimbing knives 40 with their actuating mechanism 42 are preferably arranged between the upper tubes 24b and 25b and the additional tubes 31a and 31b, and the inner of the delimbing knives 40 beyond the additional tubes 31a, 31b. The cross-cut blade 41 is preferably arranged beyond the lowest tubes 24a and 25a. In this arrangement, the delimbing knives, feed rollers, and cross-cut blade of the tree processing apparatus are in the correct order functionally and firmly attached to the harvesting unit.

The aforementioned force-applying means 15 loading the movable feed rollers 3, 4 is, for example, a spring, and preferably a hook-type spring located on the axis of tilt 16, 17, as shown in Fig. 3, and its purpose is to tilt the movable feed rollers 3, 4 to the correct angle. It is understood that other types of mechanisms may also be used. The actuating mechanisms 20, 21 of the slides are preferably hydraulic cylinders 28, 34 at least approximately parallel to the branch member, the first end 29a of the cylinders being secured to the frame part 1 at a point close to the fixed feed roller, for example, at the base of the branch members or on the base element or at their juncture. The second, moving end 30 of the hydraulic cylinder 28, 34 is secured to the slide 8, 9 for moving it in the direction Dl, D2 of the branch members, in either direction. Especially preferably the hydraulic cylinders 28, 34 are double-acting cylinders incorporating a through- going piston rod 37a, the one end 29a whereof is secured to the frame part of the harvesting unit at a point close to the fixed feed roller 2 in the aforesaid manner, and the second end 29b whereof is secured to the end 26, 27 of a tube, profile, or similar, in the branch member. The piston member 37c of the hydraulic cylinder is secured in a fixed position to the said piston rod 37a at a suitable point on its length, such as approximately in the middle. The cylinder member 37b of the hydraulic cylinder is movable on the piston 37 and through the sealed apertures in its both ends along the piston rod 37a, and joined to the said cylinder member 37b by, for example, welding, or otherwise attaching so as to be fixed, are attachment pieces 30, which in turn are joined in a fixed position by, for example, welding to the respective slides 8, 9. The attachment pieces 30 protrude from the tubes 24a, 24b, 25a, 25b, 31a, 31b or profiles in the branch member 8, 9 through narrow openings 42 in the said tubes or profiles. In this arrangement, hydraulic fluid is fed into the cylinder via conduits 43a, 43b inside the piston rod 37a, one conduit delivering the fluid to one side of the piston, the other conduit delivering the fluid to the other side of the piston. This arrangement further increases the robustness of the tubes and the construction of the branch members 8, 9, as the piston rod is secured at both ends and the cylinder element 37b is enclosed relatively tightly within the tube or profile. Further, this arrangement provides, by means of the attachment piece 30, for a large attachment surface between the actuating mechanism 20, 21 of the cylinder and the slide 8, 9 on the length of the cylinder. Further, this overall arrangement has the advantage that the said preferable hydraulic cylinder arrangement supplies the principal compressive force against the tree trunk 5, whereas the force-applying means 15 of the movable feed rollers provide for a quick response of the movable feed rollers to possible curves in the tree trunk, the combined effect being that all feed rollers retain at all times an effective contact with the surface of the tree, thus eliminating feeding problems.

Fig. 6 shows a second embodiment of the feed roller moving mechanism in cross section. Provided on the longitudinal edges of the branch member 6 are wide-flanged I-beams. The slides 8 connected to the actuating mechanism 20 move along the profiled edges in the longitudinal direction of the branch member. The movable feed roller 3 is connected to the slides 8 by means of a tube 50 and fasteners 51, thereby also making the feed roller 3 movable in the longitudinal direction of the branch member. The tube 50 may rotate about its longitudinal axis 16, whereupon the feed roller 3 is caused to tilt in the direction of rotation S or in the opposite direction in the manner illustrated in Fig. 1. The rotary movement of the tube 50 is spring-loaded. The moving mechanism provided in the branch member 7 is identical to the moving mechanism provided in the branch member 6 described above. The solution illustrated in Fig. 6 provides a robust construction.

The actuating mechanisms 20, 21 may be individual hydraulic cylinders arranged on both branch members 6, 7. In practice, however, this solution may suffer from the disadvantage that the individual cylinders are not operating simultaneously, and, consequently, the compressive force exerted by the feed rollers remains unequal. Therefore, it may be preferable to replace the actuating mechanisms 20, 21 provided individually in the branches 6, 7 with mechanically operated means actuated by one and the same hydraulic cylinder. This type of solution is shown in Figs. 7 and 8. The hydraulic cylinder 28 simultaneously actuates lever arms 59, 55, 56 and 59' (the reference number 59' is not shown, in the Figs.), 55', 56' in the branch members 6, 7. The functioning of the actuating mechanism is best illustrated in Fig 8. The lever arm 59 in combination with the lever arm 55 forms a directionally rigid construction which is rotatable about the pivot 60. The lever arm 59 is rotatable about the pivot 61. The lever arm 56, the one end 58 whereof is connected to the slide 8 by means of a joint, has its other end 57 connected to the lever arm 55 by means of a joint. When the hydraulic cylinder 28 is operated to cause the pivot 61 to move away from the base element 22, the combined arms 59, 55 turn about the pivot 60 so that the end 57 of the lever arm 55 moves closer to the base element 22, thereby pulling with it the lever arm 56 and the slide 8 connected thereto. In Fig. 8 the branch members are presented as plate-like elements, and the slide 8 is shaped to form a carriage carrying the wheels 70 and 71 along the wide-flanged I- profile of the plate-like branch member. A cross-sectional view of the solution is shown Fig. 9. Seen in relation to the height of the branch member, the tube 50 with the feed roller 3 connected thereto is located between the wheels 70 and 71. Fig. 7 shows the jointly-used hydraulic cylinder 28 and the means 55, 56, 57, 58, 60 and 55', 56', 57', 58',^* 60' located in the respective branch members 6, 7.

The invention is not in any respect limited to the most preferred embodiment described above but may embrace modifications within the scope determined by the ensuing claims. Accordingly, especially the branch members 6, 7 may, instead of consisting of tubes or profiles, also be solid structures formed by plates or other components. Similarly, the tubes or profiles that may be used may differ, or their number may vary. Further, the slides 8, 9 may have a shape and a securing arrangement different from those described above. In particular, the actuating mechanisms of the slides may vary, being, for example, pneumatic cylinders, chain drives, screw drives, or similar. In a more markedly deviant possible embodiment, the branch members 6 and 7 are so constructed as to be telescopic, in which construction one slide 8, 9 is secured in a fixed position to the end portion 26, 27 of such telescopic branch member so as to move in the direction of protrusion Dl and D2 of the branch member or in the direction opposite to this. Naturally, the said telescopic branch members 6, 7 form an acute angle K between one another, and together with their actuating mechanisms they form a rigid frame construction in conjunction with the frame part 1. Naturally, both slides are provided with feed rollers movable in the manner described above. As stated above, it should be understood that a feed roller according to the definition herein may also refer to a belt feed or a chain feed, or several feed rollers, which may be of any type suitable for the purpose.

Claims

1. A tree harvesting unit comprising a frame part (1) , a fixed feed roller (2), or similar, incorporated in the frame part, and feed rollers (3, 4), or similar, movable outwards or inwards in relation to the said fixed feed roller for moving a tree trunk (5) longitudinally (P) between and by means of the feed rollers as the feed rollers are rotated, and the means necessary for processing trees, characterized in that the frame part (1) comprises two mutually connected branch members (6, 7) of appropriate length constituting a directionally rigid frame construction and protruding from the area of the fixed feed roller (2) , thereby forming with one another an acute angle (K), that both of the branch members include at least one slide (8, 9) which is movable, principally in the direction of protrusion (Dl, D2) of the corresponding branch member, or in the direction opposite to this, and that the said movable feed roller (3 and 4) , or movable feed rollers, is secured to the slide (8 and 9, resp.) provided in each branch member, on the sides facing one another, for positioning the movable feed rollers (3, 4) against the surface of a tree trunk (5), principally by virtue of the said movement of the slides (8, 9).

2. A tree harvesting unit as claimed in claim 1, characterized in that the effective plane of rotation (10) of the fixed feed roller (2), or similar, bisects the angle ( ) between the branch members (6, 7), that the axial rotation lines (12, 13, 14) of all feed rollers (2, 3, 4) are at least approximately parallel to the plane (11) of the angle between the branch members, and that the movable feed rollers (3, 4) are secured to the slides (8, 9) so as to tilt about such axial lines (16, 17) that are in the main perpendicular to the plane (11) of the angle between the branch members.

3. A tree harvesting unit as claimed in claim 1, characterized in that the movable feed rollers (3, 4) are loaded by a force-applying means (15) to tilt about their axial lines (16, 17) in a direction of rotation (S) which, within the area of the angle (K) between the branch members (6, 7), is directed in the main towards the fixed feed roller (2), that the axial tilt lines (16, 17) of the movable feed rollers are situated adjacent to the said feed rollers with respect to the axes of rotation (13, 14) thereof, and that with the movable feed rollers (3, 4) being tilted in their extreme position by the force- applying means (15), the plane of rotation (18 and 19) of each feed roller is approximately parallel to the direction of protrusion (Dl and D2, resp.) of the corresponding branch member.

4. A tree harvesting unit as claimed in claim 1, characterized in that both branch members (6, 7) include at least one actuating mechanism (20, 21) for moving the slides (8, 9) by force towards the fixed feed roller (2) so as to press a tree trunk (5) between the feed rollers, and for returning the slides to the ends (26, 27) of the branch members with movement in the opposite direction.

5. A tree harvesting unit as claimed in claim 1, characterized in that the frame part (1) comprises a base element (22) located on the side of the fixed feed roller (2) away from the said angle (K), transversely to the plane (11) of the angle, the said base element including the support means (23) of the tree harvesting unit, that both of the branch members (6, 7) consist of at least two tubes (24a, b; 25a, b) or profiles which are located on both sides of each movable feed roller (3, 4) with respect to the length of the base element, at a distance (HI) from one another, along which tube, or tubes, or profile, or profiles, the slides (8, 9) move, and that the length (L) of the branch members (6, 7), as measured from the acting face of the fixed feed roller (2), is preferably not less than the radius (R) of the largest tree trunk (5) to be handled .

6. A tree harvesting unit as claimed in claim 5, characterized in that both branch members (6, 7) further comprise at least one tube (31a, b) or profile which is, located at a distance (H2) from and parallel to the tubes (24a, b; 25a, b) or profiles located on both sides of the feed rollers with respect to the length of the base element, that each of the said additional tubes or profiles incorporates an additional slide (32, 33) and a slide actuating mechanism (34), such as a hydraulic cylinder, for moving the slides in the direction of protrusion (Dl, D2) of the branch members, or in the direction opposite to this, and that the tree harvesting unit includes delimbing knives (40), which are connected so as to be turnable to at least the said additional slides (32, 33).

7. A tree harvesting unit as claimed in any of the claims 3-6, characterized in that each slide (8, 9) actuating mechanism (20, 21) is a hydraulic cylinder (28, 34) in the main parallel to the branch member, the first, fixed end (29a) of the hydraulic cylinder being secured to the frame part (1) in the area of the fixed feed roller (2) , and the second, movable end (30) thereof being secured to the slide for moving it in the direction (Dl, D2) of the branch member, that the movement of the slide (8, 9) is linear for the length of the branch member (6, 7) , and that each force-applying means (15) loading the movable feed rollers is a spring, preferably a hook-type spring on the axis of tilt (16, 17).

8. A tree harvesting unit as claimed in claim 5 or 7, characterized in that the slides (8, 9) provided in each branch member (6, 7) are linked to one another by means of a support bar (35, 36), or similar, parallel to the base element, and that the tree harvesting unit includes a cross-cut blade (41) for cutting tree trunks, the said cross-cut blade being connected so as to be turnable to one of the said support bars (35 or 36).

9. A tree harvesting unit as claimed in claim 6 or 7, characterized in that the hydraulic cylinders (28, 34) constituting the actuating mechanisms for the slides (8, 9) are double-acting cylinders the first end (29a) whereof, being secured to the frame part, is constituted by the one end of the piston rod (37a), the other end (29b) therof being secured to the end (26, 27) of the corresponding branch member (6, 7), and the cylinder member (37b) whereof has attached to it, by means of attachment pieces (30), the said slides, the hydraulic fluid being fed into and out of the cylinder via the hollow piston rod (37a), and that the feed rollers (2, 3, 4) are driven by hydraulic motors, the motor (38) of the fixed feed roller (2) being mounted on the frame part (1), and the motors (39) of the movable feed rollers (3, 4) being correspondingly mounted on the slides (8, 9).

10. A tree harvesting unit as claimed in any of the above claims, characterized in that the said acute angle ( ) between the branch members (6, 7) is within the range of 30°-90°, preferably in the order of 60°.

11. A tree harvesting unit as claimed in any of the above claims, characterized in that there are provided more than one fixed feed roller (2) and/or more than one movable feed roller (3, ) in each branch member (6, 7) .

12. A tree harvesting unit as claimed in any of the above claims, characterized in that the branch members (6, 7) are telescopic constructions, and that the slides (8, 9) are joined in a fixed position to the end portions of the said telescopic branch members so as to move them along with their movable feed rollers (3, 4) in the directions of protrusion (Dl and D2) of the branch members, or in the directions opposite to these.