WO2009088350A1

WO2009088350A1 - Passage cleaning machine

Info

Publication number: WO2009088350A1
Application number: PCT/SE2009/000003
Authority: WO
Inventors: Mats Rudin
Original assignee: Rudins Schakt Ab
Priority date: 2008-01-11
Filing date: 2009-01-09
Publication date: 2009-07-16
Also published as: SE531906C2; SE0800063L

Abstract

A cross-country machine for the cleaning of passages in a stand of young forest, which machine has a drive unit (1) and a felling assembly (6) with a U-shaped chassis (10) having two side beams (14,15), which are longitudinal relative to a centre plane (C) and arranged at a distance from each other for the formation of a free, open space (61) there between. The felling assembly has a width-cutting felling unit (64), from which a free, open space (65) extends vertically upwards to a level which is sufficient to allow the cut trees to fall freely backwards, inwardly toward the chassis. There is a suspension device (34), consisting of two longitudinal articulation and supporting joints (66, 67) for articulated and adjustable support of the felling unit. The felling assembly has free, open spaces (68,69,70,81,72) which together form a continuous, free, open longitudinal passage, so that the cut trees are allowed to fall freely through said passage down towards the ground.

Description

Passage cleaning machine

The present invention relates to a cross-country machine for cleaning trees in a stand of young forest in order to produce a plurality of passages of a predetermined width in the stand, while forming intermediate zones of a predetermined width between the passages.

In the present patent application, cleaning refers to a stand tending thinning of young forest, without any recovery of timber, where the average height of the predominant (dominating) and co-existent (co-dominating) trees, as a rule, does not exceed a predetermined value.

In the present patent application, cleaning of passages refers to a mechanical cleaning in a stand of young forest which results in predetermined, recurrent passages, forming openings in the stand, wherein two adjacent passages define an area therebetween, usually designated an intermediate zone, for cleaning.

Cleaning of stands of young forest takes place with an engine driven, manually carried and operated cleaning saw. Such a manual cleaning of an entire, continuous stand of trees is both labour-intensive as well as time-consuming, which in its turn results in high costs per hectare forest land in the stand.

In order to reduce the high cleaning costs by taking the underlying reasons for these costs into consideration, it is proposed that an uncleaned stand of young forest first is provided with passages of a predetermined width in order to produce zones between two adjacent, parallel or substantially parallel passages. These so called intermediate zones, having a predetermined width, are then cleaned manually with cleaning saws. The predetermined width of an intermediate zone can have a value within the interval of 5 to 8 metres, while the predetermined width of a passage has a value within the interval of 2.0 to 2.4 metres. In any case, the distance between intermediate zones should or shall substantially correspond to the distance selected for the trees remaining in the intermediate zones after the manual cleaning. The establishment of a plurality of passages in a stand of young forest creates prerequisites for the manual cleaning in the intermediate zones becoming more efficient than if the same area would have been cleaned manually without any delimiting passages. This increased efficiency is based upon the fact that it becomes easier to plan the manual cleaning operation, when the operator can utilize the passages as nearby targets, at the same time as the accessibility increases, in that the operator can move into the stand via the passages to clean the areas of the intermediate zones which are located further inside. The increased efficiency results in corresponding economic gains. A prerequisite for keeping also the total cost for the cleaning of the entire stand low, however, is that the passages can be produced with a machine in an economical and efficient way, implying (1) that the machine can be driven at a sufficiently high speed of advancement, (2) that the operational breakdowns can be kept within acceptable low limits, (3) that a satisfactory handling of the felled trees, which are to be left in the passages, is achieved, without the felled trees being accumulated in front of the felling unit with accompanying machine breakdowns, nor being deflected into the intermediate zones, where in that case they will become an obstacle to the manual cleaning, (4) that the machine has such a low weight, (4a) that no ground damages arise in the passages, (4b) that the power need for propulsion is reduced, (4c) that it is easy to transport between different cleaning sites, (5) that the felling unit can be designed and mounted in a simple way for safe cutting operation, but still is robust enough to withstand stresses from more or less solid ground objects, and (6) that machine can be manufactured at such a cost, that entrepreneurs and forest owners consider it a profitable object of investment.

Presently, there is no operating machine which meets at least a substantial part of the above-described specification of requirements.

Considering the advantages which are appreciated and expected by the forest industry from using cleaning of passages as an initial step when cleaning a stand of young forest, there is therefore a very large need to develop a machine for cleaning of passages which meets at least a substantial part of said specification of requirements .

The object of the present invention is to achieve a machine for cleaning of passages, which meets said needs and which can even meet the above-described specification of requirements in its entirety.

The machine according to the invention is characterized in that the machine comprises a wheel- or track-supported drive unit for propelling the machine, and an elongated felling assembly, which has a front end, a rear end and a centre axis, extending between said ends, wherein the drive unit and the felling assembly are articulately connected to each other, said felling assembly comprising - an elongated, U-shaped, wheel- or track-supported chassis, which is substantially symmetrical relative to a centre plane coinciding with said centre axis, said chassis comprising two longitudinal, elongated side beams and a rear transverse connection connecting the side beams, wherein the side beams have front ends forming a free opening therebetween, and are arranged at a predetermined distance from each other for the formation of a free, open space therebetween, a width-cutting felling unit having a front end, as seen in the operative driving direction of the machine, which constitutes the front end of the felling assembly, wherein a free, open space extends in a direction vertically upward from the felling unit at least up to a level which is sufficient to allow the cut trees to fall freely backwards against said driving direction, and a suspension device for pivotal suspension of the felling unit, comprising two longitudinal articulation and supporting joints for articulated and adjustable support of the felling unit, said articulation and supporting joints being arranged to extend between each side beam, in the extension thereof, and the felling unit, wherein the two articulation and supporting joints define therebetween a free, open space, merging freely into said space between the side beams, and that the felling assembly exhibits free, open spaces vertically below and above the space of the chassis, and free, open spaces vertically below and above the space of the suspension device, wherein said lower spaces extend down to the ground and said upper spaces extend to levels which are located at least slightly above the levels at which the tops of the falling trees pass by, wherein said space above the felling unit, and said spaces in connection with the chassis and the suspension device, together form a continuous, free, open longitudinal passage, which extends from a vertical plane, intersecting the front end of the felling assembly, and along the centre plane of the felling assembly and, on both sides of the same, down to the ground plane, wherein cut trees are allowed to fall freely through said passage down towards the ground.

The invention will be described further in the following with reference to the drawings.

Figure 1 shows a side view of a passage cleaning machine according to one embodiment of the invention with a drive unit and a felling assembly.

Figure 2 is a top view of the passage cleaning machine according to Figures 1 and 2.

Figure 3 shows an upper cutting element of the cutting device in Figures 1 and 2, in a view from above.

Figure 4 shows the upper cutting element in Figure 3, in a front view.

Figure 5 shows a lower cutting element of the cutting device in Figures 1 and 2, in a view from below.

Figure 6 shows the lower cutting element in Figure 5, in a view from below.

The shown cross-country machine comprises a drive unit 1 having a rear end 2 and a front end 3, as seen in the operative driving direction of the machine, for providing passages in a stand of young forest. The drive unit 1 is supported by wheels 4, driven by an engine (not shown), which also supplies different operational functions such as electronics and hydraulic equipments. Furthermore, the drive unit 1 has an operator's cab 5, and a steering gear for waist-steering of the machine. Alternatively, the supporting unit can be supported by bogie wheels or tracks. In order to obtain better visibility for the driver, the operator's cab can be arranged vertically adjustable relative to the chassis of the drive unit.

Furthermore, the machine comprises a wheel-supported, elongated felling assembly 6, which has a rear end 7 and a front end 8, as seen in the driving direction of the machine. The felling assembly 6 has a longitudinal centre axis, which extends between the rear and front ends 7, 8 thereof, and which coincides with a vertical centre plane C, as seen in the horizontal position of the felling assembly 6. The felling assembly β is articulately connected to the drive unit 1 via a universal articulation joint 9, which has one portion being connected to the front end 3 of the drive unit 1 and one portion being connected to the rear end 7 of the felling assembly 6. The felling assembly 6 comprises a horizontal, elongated, U-shaped, stable chassis 10, which is symmetrical relative to its centre plane, corresponding to the centre plane C of the felling assembly 6. The chassis 10 has a rear end, corresponding to the rear end 7 of the felling assembly 6, and a front end 11. The above-mentioned steering gear of the drive unit 1 comprises two actuators 12, such as hydraulic cylinders, which are arranged on each side of the articulation joint 9 and articulately connected to the drive unit 1 and the chassis 10. The felling assembly 6 has two wheel suspensions 13, which are mounted to the chassis 10 on each side of the centre plane C and at a distance from the same, without any common axles or other transverse connections between the wheel suspensions 13, so that thereby a free space is formed therebetween. By means of the wheel suspensions 13, the chassis 10 is maintained at a predetermined level above the ground, to prevent the chassis 10 from contacting protruding objects on the ground, such as tree stumps and stones. Such a predetermined level is normally within the interval of 30-70 centimetres and is selected depending on the ground conditions within a specific area, where the machine is to be operated.

The U-shaped chassis 10 comprises two longitudinal, elongated shanks 14, 15, and a rear transverse connection 60, connecting the shanks 14, 15 to each other. The shanks 14, 15 are formed by side beams, merging into a common, curved end beam, which constitutes said transverse connection 60 and to which said articulation portion of the articulation joint 9 and the actuator 12 are connected. The side beams 14, 15 have opposite front ends, each coinciding with said front end 11 of the chassis. Since the chassis 10 is U-shaped, it thus has a transverse opening at its front end 11, extending between the front ends of the side beams 14, 15. The space 61 defined by and extending between the side beams 14, 15 is thereby freely accessible, as seen in a horizontal plane, via said front opening of the chassis. The side beams 14, 15 are arranged at a predetermined distance from each other, which distance should be as large as possible, suitably 75-80% of the maximum width of the felling assembly 6 or machine, which in its turn is no larger than the predetermined width of the passage which is obtained.

Each wheel suspension of the chassis has a support 62, which is mounted to the associated side beams 14, 15, and two wheels, which preferably are part of a bogie wheel structure 63. Alternatively, a track-wheel structure can be used.

The felling assembly 6 further comprises a felling unit 64, and a suspension device 34 for pivotal suspension of the felling unit 64. The felling unit 64 has a front end, which constitutes said front end 8 of the felling assembly 6. The felling unit 64 is width-cutting, which means that the entire, predetermined width of the passage is produced continuously at once for each transverse, reciprocating cutting movement, without any lateral displacement of the felling unit as a whole.

The width-cutting felling unit 64 comprises a support, having two stable supporting arms 16, 17, which are arranged at a distance from each other and located in line with each side beam 14, 15, so that a free space, open in a direction upwards, is formed between them. The support further has a flat supporting plate 18, which extends horizontally between the supporting arms 16, 17 and is fixedly mounted to the lower ends of the supporting arms 16, 17. The flat supporting plate 18 has a free portion projecting from the supporting arms 16, 17 in a direction forwards, as seen in the operative driving direction of the machine, when felling of trees takes place. The felling unit 64 comprises a transverse cutting device 19, which is fixedly mounted to and supported by the supporting plate 18, which in its turn is supported by the supporting arms 16, 17. A free, open space 65 extends from the top side of the cutting device 19 and the top side of the supporting plate 18, in a direction vertically upwards to a level which is located at least slightly above the tops of the trees which are to be felled.

The suspension device 34 comprises two longitudinal articulation and supporting joints 66, 67, for articulated and adjustable support of the felling unit 64 at its supporting arms 16, 17. The two articulation and supporting joints 66, 67 extend between each side beam 14 and 15, respectively, in the extension thereof, and the supporting arm 16 and 17, respectively, which is located in this extension. The two articulation and supporting joints 66, 67 define between themselves a free, open space 68, into which the space 65 above the felling unit 64, including the space between the supporting arms 16, 17, merges freely, and which space 68 freely merges into the space 61 between the side beams 14, 15. Each articulation and supporting joint 66, 67 comprises a link arm 35 and 36, respectively, which link arm 35 and 36, respectively, is arranged on the outside of the associated supporting arm 16 and 17, respectively, and side beam 14 and 15, respectively. Each link arm 35, 36 has a lower end and an upper end. At their lower ends, the link arms 35, 36 are pivotally mounted to the supporting arms 16, 17 by means of horizontally arranged bearing bolts 37, 38, which are axially aligned with each other and located at the central portions of the supporting arms 16, 17 and at a predetermined distance from the side beams 14, 15, as seen in their extensions towards the supporting arms 16, 17. At its upper end, one link arm 36 is pivotally mounted to its associated side beam 15 by means of a horizontally arranged bearing bolt

39, while the other link arm 35 is extended upwards a predetermined length, so that its upper end becomes located above its associated side beam 14, wherein this link arm 35 is pivotally mounted to its associated side beam 14 by means of a horizontally arranged, intermediate bearing bolt 40, which is located at the same distance from the bearing bolt 39 at the lower link arm end as for the bearing bolts 38, 39 of the first-mentioned link arm 36. The extended link arm 35 thereby constitutes a lever which is pivotally about its intermediate bearing bolt

40. The bearing bolts 39, 40 of the link arms 35, 36, which are arranged at the side beams 14, 15, are axially aligned with each other. An actuator 41, in the form of a hydraulic cylinder, has its piston rod end articulately connected to the upper end of said second link arm 35, and its cylinder end articulately connected to its associated side beam 14. When actuating the hydraulic cylinder 41 to retract its piston rod, the felling unit 64 will be pivoted upward to an upper transport position (not shown) from the lower operative position shown. In an alternative embodiment, the first-mentioned link arm 36 is designed and provided with a hydraulic cylinder in the same way as the last-mentioned link arm 35.

Furthermore, each articulation and supporting joint 66, 67 comprises an actuator 42 and 43, respectively, in the form of a hydraulic cylinder, which constitutes an upper connection between the associated side beam 14 and 15, respectively, and the supporting arm 16 and 17, respectively. Each hydraulic cylinder 42, 43 has its cylinder articulately mounted to the free end of the side beam 14, 15 by means of a horizontal bearing bolt 45, and its piston rod articulately mounted to the upper end of the opposite supporting arm 16, 17 by means of a horizontal bearing bolt 46. The two bearing bolts 45 are axially aligned with the bearing bolts 40, 39 of the link arms 35, 36. When actuating the hydraulic cylinders 42, 43, the support 16, 17, 18 and the cutting device 19 of the felling unit are pivoted in the desired direction about the pivot axis formed by the two bearing bolts 37, 38, which articulately connect the link arms 35, 36 to the supporting arms 16, 17. When the piston rods are extended outward in a direction from the side beams 14, 15, the cutting device 19 will thus be pivoted downward to a non-inclined working position, the height of which above the ground surface is adjusted with the link arms 35, 36 and the associated hydraulic cylinder 41. At least one of the two hydraulic cylinders 42, 43 is provided with a pressure sensing valve (not shown) which breaks an electrical circuit when the pressure in the selected hydraulic cylinder 42 or 43 rises above a predetermined level. This electrical circuit is connected in series with the pilot circuit of the drive unit 1. When the cutting device 19 hits an obstacle, such as, for example, a stone or an oversized tree trunk, the pressure in the hydraulic cylinders 42, 43 rises and the valve breaks the electrical circuit and the passage cleaning machine stops. If the obstacle is an oversized tree trunk, the trunk is cut off with repeated cutting movements, and the machine then automatically continues to advance into the tree stand. If the obstacle is a solid object, the machine operator has to actuate the hydraulic cylinder 41 to lift the cutting device 19 over the obstacle, to then be able to continue. The disclosed arrangement thus constitutes an anti-collision protection system, which has the purpose of protecting the cutting device 19 and its attachments from deformation when the cutting device 19 hits a solid obstacle.

The cutting device 19 is constituted of a so-called cutting beam or knife beam and comprises an upper, movable cutting element 20 and a lower, fixed cutting element 21, which cutting elements 20, 21 are shown more closely in Figures 3 to 6. The lower cutting element 21 is fixedly mounted to said free portion of the supporting plate 18, while the upper cutting element 20 is movably mounted to the lower, fixed cutting element 21, so that the upper, movable cutting element 20 can be moved back and forth, in its longitudinal direction, in the horizontal plane transversely to the cutting direction.

The upper and lower cutting elements 20, 21 are flat and have lengths determining the cutting width. Accordingly, the cutting elements 20, 21 extend transversely to the cutting direction of the passage cleaning machine and perpendicularly to the centre plane C of the felling assembly.

In an alternative embodiment (not shown) of the cutting device, comprising a lower, fixed cutting element, e.g. similar to the one shown, the movable cutting element consists of an endless cutting chain, in which the cutters are articulately connected to one another via intermediate link means having vertical pivot axes, so that the cutters are located in a horizontal plane, wherein the cutting chain is rotatably journalled at the two ends of the cutting device by means of suitable sprocket wheels, around which the cutting chain travels in a horizontal plane, wherein a leading portion of the cutting chain is in cutting cooperation with the fixed cutting element and a trailing portion moves in the opposite direction at a suitable distance behind the leading portion, said trailing portion, as well as the side portions of the cutting chain travelling around the sprockets, being protected by a suitable cover. The driving of the cutting chain takes place by means of a hydraulic motor via a transmission, e.g. via one or both of the sprocket wheels and engagement members, e.g. gear teeth of suitable types. Suitably, there are supporting rollers and/or supporting grooves inside the cutting chain loop, for supporting the cutting chain.

As is shown in Figures 1, 4 and 6, the cutting elements have flat surfaces 52, 53, facing against each other for slidable cooperation with each other, wherein the interface between them is supplied with lubricant via not shown lubricating nipples .

As is shown in Figure 3, the upper, movable cutting element 20 comprises a plurality of cutting blades 22, extending in parallel with each other in the cutting direction and thus perpendicularly to the longitudinal direction of the cutting device 19. Each cutting blade 22 has flat bottom side and has its top side formed with two edge-forming lateral surfaces 23, 24, facing away from each other and terminating in sharp edges. The cutting blades 22 are arranged at a predetermined distance from each other, wherein open, U-shaped spaces 25 are formed between the cutting blades 22, which spaces 25 extend into the cutting element 20 for the formation of an inner curved rim, which is bevelled to an edge 26. Each cutting blade 22 carries a guide pin 27, projecting in the longitudinal direction of the cutting blade 22, which guide pins 27 are adapted to guide the trees into the spaces 25 between the cutting blades. As is shown in Figures 3 and 4, the guide pins 27 are round, preferably circular, and also have rounded ends. Accordingly, the guide pins 27 are completely free of sharp lateral edges and of sharp tips, which edges and tips could penetrate into the tree trunks which the guide pins 27 come into contact with. When a guide pin 27 contacts an oncoming tree trunk with its rounded end, the relatively thin tree trunk will be deflected laterally by the guide pin 27, as the tree trunk is flexible, to subsequently be received in the space 31, towards which the guide pin 27 and its cutting blade is moving. The deflection of the tree trunk is facilitated or enabled when the cutting device 19 is located at a certain distance above the ground.

As is shown in Figure 5, also the lower, fixed cutting element 21, shown from below, comprises a plurality of cutting blades 28, extending in parallel with each other in the cutting direction and thus perpendicularly to the longitudinal direction of the cutting device 19. Each cutting blade 28 has a flat top side and has its bottom side formed with two edge-forming lateral surfaces 29,

30, facing away from each other and terminating in sharp edges. The cutting blades 28 are arranged at a predetermined distance from each other, wherein open, U-shaped spaces 31 are formed between the cutting blades 28, said spaces 31 extending into the cutting element 21 for the formation of an inner curved rim, which is bevelled to an edge 32. The cutting blades 28 have free ends which are straight (situated on the same line) and suitably bevelled. Accordingly, the ends lack sharp tips, which could penetrate into an oncoming tree trunk. The spaces 25 and 31 of the two cutting elements 20, 21 are equally large, and the width between two cutting blades 22; 28 of the respective cutting element 20, 21 is larger than the width of one cutting blade 22; 28. The width of the spaces 25, 31 is adapted to the size of the tree trunks. The lower cutting element 21 is fixedly mounted to the supporting plate 18, while the upper cutting element 20 is arranged movably relative to the lower cutting element 21 in a reciprocating motion transversely to the cutting direction. For this purpose, the lower, fixed cutting element 21 is provided with a plurality of elongated, through-going guide slots 54, extending in the longitudinal direction of the cutting element 21, wherein the upper, movable cutting element 20 has a corresponding number of through-going holes 55 which, in the mounted cutting device 19, are aligned with the guide slots 54. Thereby, the cutting elements 20, 21 are connected to each other by means of bearing bolts 56, which extend through the holes 55 and the elongated guide slots 54, and which are secured by means of locking nuts. In operation, the upper cutting element 20 moves back and forth in the longitudinal direction of the cutting device 19 in such a way that the cutting blades 22 of the upper cutting element 20 and the cutting blades 28 of the lower cutting element 21 pass by each other in a lapping relationship and in contact with each other, to obtain a shearing or cutting action. The reciprocating movements of the upper, movable cutting element 20 are achieved by means of an actuator 33 in the form of a double-acting hydraulic cylinder, the cylinder portion of which is placed in a recess 57 on the back side of the lower, fixed cutting element 21, wherein the end surfaces of the recess 57 form supports for the ends of the cylinder portion. The double-acting hydraulic cylinder 33 has a through-going piston rod (see Figure 1), both ends of which are fixedly mounted to two lugs 58 of the upper cutting element 20. In an alternative embodiment, the actuator for driving the movable cutting element is constituted of a connecting rod assembly, which is driven by a motor, e.g. a hydraulic motor.

The reciprocating movements of the upper cutting element 20 are controlled by electronic sensors (not shown) , emitting a signal to an electronic unit (not shown) , which controls an electrical valve (not shown) . In an alternative embodiment, the reciprocating movements of the upper cutting element 20 are controlled mechanically with pivot valves (not shown) .

By means of the suspension device 34, the cutting device is adjusted to a suitable level above the ground, depending on the character of the ground, such as from 5 centimetres for even ground, up to 40 centimetres for very uneven or broken ground.

The two continuous spaces 61, 68, i.e. spaces merging freely into one another, being defined between the side beams 14, 15 and the articulation and supporting joints 66, 67, define lower spaces 69, 70 extending vertically downward towards the ground, and upper spaces 71, 72 extending vertically upward, which spaces together form an entirely free and open passage, extending in the centre plane C and on both sides thereof from the felling point, which is defined by the felling assembly 6, to the rear portion of the chassis 10, so that the cut trees can fall freely backwards through the entirely free and open passage, which extends further through the chassis 10, in order to be accumulated on the ground in an orderly row over which, in addition, the drive unit 1 can pass without any problem. This orderly accumulation of the falling trees on the ground is thus enabled in that the felling assembly 6 is free of transverse structural elements passing through the centre plane C and which would therefore interfere with or preclude operation. In the embodiment shown, the chassis 10 supports a transverse sawing device, which comprises a saw bar 50, and which extends between the side beams 14, 15 and is mounted to the rear end portions of the side beams 14, 15. The saw bar 50 carries a saw chain 51, extending and travelling around the circumference of the saw bar 50. The saw chain 51 is driven by an actuator in the form of a hydraulic motor (not shown) and is adapted to cut off the tops of the cut, longer tree trunks which fall down in a direction towards the rear portion of the chassis 10. Accordingly, the sawing device is not an operationally disturbing structural member but is, on the contrary, a valuable aid for preventing trees, particularly longer trees, from being pushed up towards the operator's cab 5 and laterally outside the sides of the chassis 10. Alternatively, the sawing device can be mounted on two vertical posts, projecting from each side beam, and along which the sawing device can be lowered and raised to be moved between an upper resting position and a lower sawing position.

The space below the drive unit 1 of the machine is sufficiently large in a vertical direction to enable the trees cut and accumulated on the ground, which have fallen down between the side beams 14, 15, to be by-passed by the drive unit 1 without any problem. If desired, the drive unit 1 can be equipped with a device for processing the row of trees, while the drive unit 1 is advancing, e.g. a pressing device, such as a roll or cylinder, or a disintegrator for disintegrating the trees to bio-fuel, which is collected.

If desired, an operator's cab can be arranged on the chassis, from which operator's cab the passage cleaning machine is operated during the felling operation. The operator' s cab is placed so that it does not constitute an obstacle to the falling trees, e.g. at one of the side beams and at a suitable distance above the same.

With advantage, the passage cleaning machine can be equipped with GPS and a software making it possible to follow the passages on a digital map material, where the position is recorded. This enables the machine operator to find the way more easily in the terrain. Also other variants, having only a GPS transmitter, are conceivable. The GPS transmitter then sends data to an external GPS receiver for processing the extensions and positions of the passages, which facilitates the manual cleaning in the resulting intermediate zones.

In the foregoing, the invention has been described with reference to a specific embodiment. It is appreciated that other embodiments and variants are possible within the scope of the following claims. For instance, the end portion of the chassis 10 can be straight or V-shaped instead of curved. Furthermore, the cutting device and the supporting arms can alternatively be movable up and down on a support, which is pivotally suspended from the support beams 14, 15.

Claims

C L A I M S

1. A cross-country machine for cleaning trees in a stand of young forest in order to produce a plurality of passages of a predetermined width in the stand, while forming intermediate zones of a predetermined width between the passages, characterized in that the machine comprises a wheel- or track-supported drive unit (1) for propelling the machine, and an elongated felling assembly (β), which has a front end (8), a rear end (7) and a centre axis, extending between said ends (7, 8), wherein the drive unit (1) and the felling assembly (6) are articulately connected to each other, said felling assembly (6) comprising an elongated, U-shaped, wheel- or track-supported chassis (10), which is substantially symmetrical relative to a centre plane (C) coinciding with said centre axis, said chassis (10) comprising two longitudinal, elongated side beams (14, 15) and a rear transverse connection (60) connecting the side beams, wherein the side beams (14, 15) have front ends (11) forming a free opening therebetween, and are arranged at a predetermined distance from each other for the formation of a free, open space (61) therebetween, a width-cutting felling unit (64) having a front end, as seen in the operative driving direction of the machine, which constitutes the front end (8) of the felling assembly (6), wherein a free, open space (65) extends in a direction vertically upward from the felling unit (64) at least up to a level which is sufficient to allow the cut trees to fall freely backwards against said driving direction, and - a suspension device (34) for pivotal suspension of the felling unit (64), comprising two longitudinal articulation and supporting joints (66, 67) for articulated and adjustable support of the felling unit (64), said articulation and supporting joints (66, 67) being arranged to extend between each side beam

(14, 15), in the extension thereof, and the felling unit (64), wherein the two articulation and supporting joints (66, 67) define therebetween a free, open space (68), merging freely into said space (61) between the side beams (14, 15), and that the felling assembly (6) exhibits free, open spaces (69, 71) vertically below and above the space (61) of the chassis (10), and free, open spaces (70, 72) vertically below and above the space (68) of the suspension device (34), wherein said lower spaces (69, 70) extend down to the ground and said upper spaces (71, 72) extend to levels which are located at least slightly above the levels at which the tops of the falling trees pass by, wherein said space (65) above the felling unit (64), and said spaces (65, 70, 68, 72, 69, 61, 71) in connection with the chassis (10) and the suspension device (34), together form a continuous, free, open longitudinal passage, which extends from a vertical plane, intersecting the front end of the felling assembly (6), and along the centre plane (C) of the felling assembly (6) and, on both sides of the same, down to the ground plane, wherein cut trees are allowed to fall freely through said passage down towards the ground.

2. The cross-country machine according to claim 1, characterized in that said passage has a horizontal extension, as measured at the level of the side beams (14, 15), which is adapted to the height of the trees included in the stand in question, which is to be prepared for cleaning, that the felling unit (64), as seen perpendicularly to the centre pane (C) , has a length which is equal to the predetermined width of the passage which is to be formed, that the machine has a width which is equal to and preferably slightly smaller that the length of the felling unit (64), and that the distance between the side beams (14, 15) is as large as possible.

3. The cross-country machine according to claim 2, characterized in that said horizontal extension of the passage is about 4 metres at the most and is selected in dependence of the height of the trees of the stand, that the length of the felling unit (64) is 2.40 metres, and that the distance between the side beams (14, 15) is 75-80% of the maximum width of the machine.

4. The cross-country machine according to any one of the claims 1-3, characterized in that the felling unit (64) comprises - an elongated cutting device (19) , which is arranged transversely to the driving direction of the machine, and an actuator (33) for controlled driving of the cutting device (19), and - that the cutting device (19) comprises an upper, movable cutting element (20), and a lower, fixed cutting element (21) , said cutting elements (20, 21) being arranged in a cutting relationship to one another.

5. The cross-country machine according to claim 4, characterized in that the cutting device (19) is constituted of a cutting beam, the upper cutting element (20) of which is movably mounted relative to the lower, fixed cutting element (21) .

6. The cross-country machine according to claim 5, characterized in that the upper, movable cutting element

(20) is adapted to be moved back and forth, in its longitudinal direction, in the horizontal plane transversely to the driving direction.

7. The cross-country machine according to any one of the claims 4-6, characterized in that the upper and lower cutting elements (20, 21) have flat surfaces (52, 53) , which are in sliding engagement with each other.

8. The cross-country machine according to any one of the claims 4-7, characterized in that the upper, movable cutting element (20) comprises a plurality of cutting blades (22), extending in parallel with each other in the cutting direction of the machine, wherein each cutting blade (22) has a flat bottom side and has its top side formed with two edge-forming lateral surfaces (23, 24), facing away from each other, and that the cutting blades (22) are arranged at a predetermined distance from each other, wherein open, U-shaped spaces (25) are formed between the cutting blades (22) , said spaces (25) extending into the cutting element (20) for the formation of an inner curved rim, which is bevelled to an edge (26) .

9. The cross-country machine according to any one of the claims 4-8, characterized in that the lower, fixed cutting element (21) comprises a plurality of cutting blades (28), extending in parallel with each other in the cutting direction of the machine, wherein each cutting blade (28) has a flat bottom side and has its top side formed with two edge-forming lateral surfaces (29, 30), facing away from each other, and that the cutting blades (28) are arranged at a predetermined distance from each other, wherein open, U-shaped spaces (31) are formed between the cutting blades (28) , said spaces (31) extending into the cutting element (21) for the formation of an inner curved rim, which is bevelled to an edge (32) .

10. The cross-country machine according to any one of the claims 8 and 9, characterized in that each cutting blade (22) of the upper, movable cutting element (20) carries a guide pin (27), said guide pins extending in the longitudinal direction of the cutting blade (22) and being adapted to guide oncoming tree trunks into the spaces (25, 31) between the cooperating cutting blades (22, 28) during the movement of the upper cutting element (20) relative to the lower cutting element (21) , wherein the guide pins (27) are round and have rounded ends and the cutting blades (28) have free ends which are straight and bevelled.

11. The cross-country machine according to any one of the claims 2-10, characterized in that the actuator (33) for the reciprocating movements of the upper cutting element (20) is constituted of a double-acting hydraulic cylinder having a through-going piston rod.

12. The cross-country machine according to any one of the claims 4-11, characterized in that the drive equipment comprises electronic sensors, emitting a signal to an electronics unit, which controls an electrical valve in order to control the reciprocating movements of the upper cutting element (20) .

13. The cross-country machine according to any one of the claims 4-11, characterized in that the drive equipment comprises pilot valves adapted to mechanically control the reciprocating movements of the upper cutting element (20) .

14. The cross-country machine according to any one of the claims 1-13, characterized in that the felling unit (64) comprises a support, comprising two supporting arms (16, 17) being arranged at a distance from each other and located in line with each side beam (14, 15), and a flat supporting plate (18), supporting the cutting device (19) •

15. The cross-country machine according to claim 14, characterized in that each articulation and supporting joint (66, 67) comprises a link arm (35 and 36, respectively) , said link arms (35, 36) being arranged on the outsides of and pivotally mounted to the supporting arms (16, 17) and the side beams (14, 15) .

16. The cross-country machine according to any one of the claims 14 and 15, characterized in that two actuators (42, 43), in the form of hydraulic cylinders, constitute upper connections between the side beams (14, 15) and the supporting arms (16, 17), so that the cutting device (19) can be pivoted to the desired working position, wherein at least one of the two hydraulic cylinders (42, 43) is provided with a pressure sensing valve, which breaks an electrical circuit when the pressure in the hydraulic cylinder (42; 43) rises above a predetermined level, said electrical circuit being connected in series with the pilot circuit of the drive unit (1), so that the drive unit (1) stops, when the electrical circuit is broken.

17. The cross-country machine according to any one of the claims 15 and 16, characterized in that one hydraulic cylinder has its piston rod end articulately connected to the upper end of one link arm (35) , and its cylinder end articulately connected to its associated side beam (14) .

18. The cross-country machine according to any one of the claims 1-17, characterized in that the chassis (10) supports a transverse sawing device, comprising a saw bar (50), which extends between the side beams (14, 15) or is vertically adjustable between two posts, projecting from each side beam.