WO2011090419A1

WO2011090419A1 - Device and method for felling and cutting tree trunks

Info

Publication number: WO2011090419A1
Application number: PCT/SE2011/000010
Authority: WO
Inventors: Sverre Aronsson
Original assignee: Sverre Aronsson
Priority date: 2010-01-23
Filing date: 2011-01-22
Publication date: 2011-07-28
Also published as: SE535915C2; EP2542046A4; SE1000064A1; EP2542046A1

Abstract

The present invention concerns a harvester head (1) for felling and cutting elongated tree trunks (2) including at least one frame (6) fitted with at least one gripping device (9) and at least one feeder device (15) and one cutting device (18) with a chain saw bar (20) that is rotatable around a first swing axel (22). The present invention's uniqueness comes from that the harvester head (1) includes at least one, after the cutting device (18), trailing spacing wedge (23) which is maneuvered forwards and backwards into the saw notch in a motion that is relative to the cutting device (18) and essentially perpendicular with the harvester head's and tree trunk's central axis, which is intended to hinder pinching of the chain saw bar (20) and minimize stress cracks in the cut logs. Furthermore the present invention includes a method for using the harvester head (1) in accordance with the invention.

Description

Device and Method for Felling and Cutting Tree Trunks

Field of the Invention

The present invention relates to a device and method for felling and cutting tree trunks (timber) with the purpose of reducing the occurrence of so called stress cracks. More specifically, the present invention is intended for a harvester head (processing head) and a method for using a said head in accordance with the claims.

Background of the Invention

In today's mechanized forestry the felling, de-branching and cutting of tree trunks are predominantly done using harvester vehicles or the like. The harvester is equipped with a crane arm (boom) onto which on its outermost extension a rotating and swiveling harvester head is mounted. By using this one and only harvester head a tree trunk is felled, de-branched and cut into logs. During felling, after the tree trunk is separated from its root base, the tree trunk during de-branching is essentially horizontally fed through the harvester head. After a certain length of the tree trunk is de-branched, the protruding part of the trunk is cut (sawed) off with a cutting device for example a chain saw bar which cuts into the tree trunk starting from the upper facing side of the trunk and continuing in an essentially vertical direction downwards through the entire trunk.

When cutting takes place in this fashion, stress cracks are created in the log. Stress cracks are created because of the weight of the protruding trunk bends the tree trunk during cutting. This bending phenomenon causes the log to partially split in its elongated direction before the cutting process is complete.

The presence of cracks caused by harvesting greatly impacts the value of timber in a negative manner. The Forestry Research Institute of Sweden, in their newspaper "Resultat" (#19, 1999) stated that 40 to 70 percent of all forested logs showed signs of cracking. The article further reveals that the logs that show the greatest damage are the most valuable larger and longer ones.

A number of techniques have been developed to reduce the occurrence of cracks in timber logs during cutting. The easiest way to reduce the frequency of cracks is to support the hanging part of the tree trunk during the cutting process. However, cutting using support techniques takes longer and reduces the effectiveness of the harvest. The Forestry Research Institute of Sweden estimates that it takes ten percent longer to cut a single log using support. Another method to reduce cracking is to reduce the cut log's falling angle by the operator lowering the crane arm (boom) and the harvester head during the last moments of the cut. However, this requires a lot of skill from the operator and can hardly be recommended procedure for the industry. This is because the crane arm (boom) must be lowered at precisely the right moment and the cut must be timed just right using the correct speed in order to be effective. If this lowering is started too soon, the maneuvering room in height for larger logs will be too small. If this lowering is done too quickly, the cutting device (chain saw bar or similar) can get pinched in the log. If lowering is concluded too soon during the cut, cracking will appear, even with the smallest of logs. There exits an automatic system for crane arm (boom) lowering which has been developed by the forestry machine manufacturer Ponsse. This system for crane arm (boom) lowering has the disadvantage of causing the operator's box to shift position during the lowering process. This has resulted in operators disconnecting the system and in so doing the intended effect is not achieved.

Earlier, it has also been shown that cutting speed also affects the number of stress cracks found in logs. There are fewer cracks made when cutting is done at higher speeds. It is also well known that the numbers of cracks are minimized by how sharp the cutting device is.

In the process of felling trees using a harvester head, a number of other problems occur. In order to avoid having the cutting device getting stuck in the tree trunk during the first felling cut, the operator often has to apply a certain amount of opposite force to the tree. However, this also creates bending stress at the point of the cut which increases the chance of splitting. Further, the risk of getting the cutting device stuck during felling reduces the maximum possible cutting speed for the cutting device.

Attempting to cut the log from the bottom facing side in connection with bucking, also causes problems. These problems consist mainly of the risk of the cutting device getting stuck in the log during the cut. A stuck cutting device increases the risk of accidents and damage, as for example slung saw chains, damage to cutting teeth or other types of damage.

Prior Art

One method for cutting freely hanging horizontal objects that are sensitive to splitting, for example de branched tree trunks, is earlier known via patent SE450356. This method is intended for reducing the occurrence of cracks at the point of the cut. This method uses a cutting device that has an endless circulating guided saw chain whose top cutting edge is applied to the underside of the tree trunk and then upwards through the tree trunk. This design solves the present problem by only having one part of the cutting device inserted in the timber during the cut. During cutting the freely suspended log's lower edge is affected by the tensional stress which forces the two pieces against each other. Towards the end of the cutting process, the part of the tree trunk that has not completely been sawed through is only exposed to short-duration tensional stress, but essentially no bending stress. The design is however, vastly different then this present invention because it lacks a trailing spacing wedge. Cutting is also not accomplished using a single grip harvester head. Furthermore the design according to the patent can not be used for felling rooted, vertical tree trunks. The design prohibits an easy integration to an existing harvester head.

Single grip harvester heads have long been known and exist in many configurations and embodiments. For example the Swedish patents SE530133, SE531644 and others describe this type of harvester heads. However, none of these existing patents offer an after the chain saw blade trailing spacing wedge intended to reduce the creation of stress cracks.

In US 3636996 Al is described a pinching support arm intended to support a log during cutting. The described arm is placed under the log to be cut and the chain saw bar saws down toward the arm. Said arm does not follow the chain saw bar from the top side of the log into the saw notch. This design does not eliminate the occurrence of stress cracks and in all probability even worsens stress cracks in a sawed log and only alleviates pinching in proximity to an underlying surface, relying on said surface for support. This design differs substantially from the present invention.

In US 5074047 is described an anti-pinch device for chain saws intended stop upward cutting (under bucking) through a log that is to say to start cutting from the bottom side of the log. This design does not eliminate the occurrence of stress cracks and in all probability even worsens stress cracks in a sawed log. This design is also only intended to eliminate pinching when sawing from above so called over bucking. This design differs substantially from the present invention.

Detailed Description of the Invention

The invention will be described in greater detail below with reference to the accompanying schematic drawings that in an exemplifying purpose show the current preferred embodiments of the invention.

Figure 1 shows in perspective a schematic view of a harvester head with a spacing wedge in accordance with one embodiment of the present invention. Figure 2 shows a schematic view of a harvester head with a spacing wedge in accordance with an embodiment in accordance with a second exemplifying embodiment of the present invention.

Figures 3 - 7 show cutting with a harvester head equipped with a spacing wedge in accordance the present invention.

Figure 8 shows a schematic view of an exemplifying form of the trailing spacing wedge.

With reference to the figures and more specifically to figures 1 to 3 is shown a schematic view of a harvester head 1 intended to be used for felling, de-branching and cutting tree trunks 2.

In alternative embodiments it is conceivable that the harvester head only be intended for felling or cutting or a combination of felling and cutting. The harvester head 1 is preferably mounted, or otherwise suitably attached, via at least one swivel 3 and at least one mounting bracket 4 or similar device to (in) the end (outermost part) 5 of the crane arm (boom) of a forestry harvester (not shown in the figures). Alternatively the harvester head 1 can be attached to and maneuvered by another type of vehicle (machine) or device that is suited for the task.

The harvester head 1 comprises a design that is based upon existing single grip harvester heads 1 which is equipped with at least one spacing wedge in accordance with the present invention.

The exemplifying embodiment of the harvester head 1 shown in the figures is just one of many conceivable designs for the harvester head which is possible within the scope of the present invention's scope of protection.

In the exemplifying embodiment of the harvester head 1 , it includes a frame 6 that via at least one joint 7 is pivotally arranged in relation to at least one tip arm 8. The tip arm 8 is, via the swivel 3, connected to the mounting bracket 4 which in turn is mounted to the end 5 of the crane (boom) arm. Using the swivel 3 the tip arm (and the entire harvester head) can rotate around the vertical axel shown in the figures from the end of the crane (boom) arm to the swivel. Using the joint 7 the frame 6 can maneuver (rotate) around an essentially horizontal axis shown in the figures. The frame can be maneuvered between an essentially vertical position during the felling of a tree to an essentially horizontal position during the de- branching and cutting of the felled tree. The frame 6 has at least one gripping device 9 with which the tree trunk is gripped. The gripping device 9 in the exemplifying embodiment includes a first gripper 10, a second gripper 11, a third gripper 12 and a fourth gripper 13. The grippers 10-13 consist preferably of a grip claws or similar design that is suited for the task. The grippers, are in accordance with earlier known technology, pivotally arranged and preferably maneuvered with at least one maneuvering organ that in the exemplifying embodiment consists of a hydraulic cylinder. In alternative embodiments the maneuvering of the grip claws can be done using other for the purpose suitable technical solutions, for example some type of electrically driven

maneuvering organ.

The harvester head 1 also includes at least one de-branching organ 14. The de-branching organ 14 includes preferably at least one de-branching knife, or de-branching blade or similar. These de-branching knifes are preferably integrated with one or more of the grip claws 10-13. One or more of these de-branching knifes may also be mounted on another for the purpose suitable part of the frame (6) or another location on the harvester head that is suited for the task.

The harvester head 1 also includes at least one feeder device 15. The feeder device 15 in the exemplifying embodiment includes a first feeding organ 16 and preferably at least a first feeding organ 16 and a second feeding organ 17. The feeding organs in the figures consist of feeding-in rollers (feed rolls) of some earlier known type and therefore will not be described more specifically in this patent application. The first feed roller and the second feed roller are pivotally (rotatable) arranged in relation to the frame 6. Each respective roller is driven by an appropriate for the purpose drive unit. The drive unit is preferably hydraulically driven. It is conceivable that the drive unit in alternative embodiments consist of an electric drive unit or another for the purpose suitable type of drive unit.

The exemplified harvester head also includes at least one cutting (sawing) device 18 which is preferably placed on the lower section of the harvester head. Preferably, the cutting device 18 includes a chain saw 19 with a chain saw bar 20 and a cutting chain 21 that is mounted in a chain saw enclosure. The figure does not show the protective cover that is usually mounted to the saw enclosure which protects the saw when it is in the enclosure. The chain saw bar 20 is arranged to rotate outwardly in relation to a swing axel 22 (fulcrum) in the harvester head's essentially axial direction. The chain saw bar, along with its associated cutting chain, is maneuvered using existing techniques, and therefore the design will not be described further in this patent application. The chain saw bar's 20 positioning, its turning in relation to its swing axel and the cutting chain's 21 powered movement is preferably accomplished by hydraulics. In alternative embodiments it is conceivable that these functions may be powered using other technical solutions appropriate for the purpose, for example electrically or other for the purpose suitable power.

What is unique about the present invention is that the harvester head 1 includes at least one, after the chain saw bar 20, trailing spacing wedge 23 that reduces the risk of, or prevents the occurrence of, the chain saw bar getting stuck in the sawing notch during sawing, and also prevents the creation of stress cracks in the logs during the final cutting stage. The trailing spacing wedge 23 is maneuverable in a transverse direction in relation to the harvester head's (and tree trunk's) axial position. Maneuvering the spacing wedge 23 can be accomplished by rotating it against the tree trunk in the same fashion as the chain saw bar. Maneuvering can in alternative embodiments be accomplished by moving the spacing wedge 23 in an essentially radial direction relative the harvester head's (and tree trunk's) center axis. It is also conceivable that the trailing spacing wedge 23 during movement in towards the sawing notch, is turned at an angle relative to the harvester head's and tree trunk's center axis. In alternative embodiments the movement of the spacing wedge in the direction in towards the harvester head's center axis, can be accomplished using other, for the purpose, suitable methods, such as a rotating motion for example by an angular change in relation to the tree trunk's axial center.

In the preferred embodiment the spacing wedge 23 is arranged to rotate in toward and away from the harvester head's and tree trunk's axial center. In the preferred embodiment the spacing wedge 23 is arranged to rotate around a swing axel (revolving axel, spin axis) 24. Preferably, the spacing wedge's swing axel (spin axis) 24 runs parallel in relation to the chain saw bar's swing axel (spin axis) 22. In the preferred embodiment of the present invention, both the spacing wedge 23 and the chain saw bar (20) are arranged to rotate (swing) out using a common axel, that is to say that both axels 22 and 24 coincide or essentially coincide. In alternative embodiment of the present invention, it is conceivable that the chain saw bar's swing axel 22 and the spacing wedge's swing axel 23 are separated and therefore do not coincide. The spacing wedge 23 is preferably attached to the swing axel 24 via a swivel connection 25 or similar. The swivel connection 25 is preferably consists of, or includes, at least one slip clutch or similar device that, at a specific amount of force or torque, allows the spacing wedge 23 to rotate relative to the swing axel (revolving axel) 24. The maneuvering of the spacing wedge 23 is preferably accomplished by hydraulics. In alternative embodiments it is conceivable that maneuvering can be accomplished electrically or by using other powering solutions suitable for the purpose.

Figures 3-7 show schematic views of the cutting process using a harvester head in accordance with the present invention. Preferably, cutting is done directly after the tree is felled. During cutting and de-branching, the tree trunk 2 is fed through the harvester head in a horizontal direction (or essentially a horizontal direction). After a certain length of the tree trunk 2 is de- branched, the protruding (or free hanging) part of the trunk 26 is sawed off from the gripped (or not free hanging) part of the trunk 27. In the exemplifying figures, the chain saw bar 20 is inserted into the tree trunk (2) essentially from the bottom side. In the second exemplifying embodiment of the harvester head according to figure 2, the trailing spacing wedge is inserted in from the side of the tree trunk. This is different compared with the traditional way of using known harvester heads where the chain saw bar is essentially inserted into the tree trunk from the top side. Figure 3 shows a harvester head positioning the tree trunk to the position desired for cutting. In figure 4, the cutting has started by rotating the chain saw bar around its swing axel (rotation point) in toward the tree trunk and then begins to saw a cut into the tree trunk. The cutting continues by further rotating the chain saw bar into the tree trunk. During the cut, the chain saw bar creates an essentially straight notch in the log that preferably continues perpendicular to the tree trunk's direction. In figure 4 the trailing spacing wedge has not yet been inserted into the saw notch.

In figures 5 and 6 the chain saw bar is shown in different positions during the tree trunk cutting process. The trailing spacing wedge 23 is shown partially inserted into the saw notch. Once the trailing spacing wedge is inserted into the saw notch, the desired technical effect is achieved; the bending stress and therefore the pinching force of the free hanging tree trunk (from the unfinished section of the cut) is reduced. The bending force tension is essentially transferred to the unfinished section of the cut.

The form of the spacing wedge may vary substantially within the scope of the present invention. In figure 8 the preferred embodiment of the present invention is shown, where the spacing wedge has an L-shaped cross-section. The spacing wedge 23 with the L-shaped cross-section includes a first part 28 and a second part 29. The first part 28 is intended to be partially or completely inserted into the saw notch. The second part 29 is intended to act as a stop and when used as part of the spacing wedge 23 the part 29 will rest against the outside of the tree trunk, the part of the trunk that is gripped by harvester head 1. The spacing wedge 23 with the L-shaped cross-section provides specific technical effects beyond the obvious stop function. Because the first part 28 is parallel with the cut, the cut free hanging log, when it falls away, will glide off the spacing wedge 23 without damaging it. Furthermore the spacing wedge 23 will help protect the remaining log from being damaged by the cut free hanging log as it falls away. In alternative embodiments it is conceivable that the spacing wedge's cross- section has another for the purpose suitable form. For example, it may be square, rectangular, triangular, wedge shaped or of another for the purpose suitable form.

The form of the trailing spacing wedge 23, seen from the harvester head's 1 and tree trunk's directional axis, can vary widely within the scope of the present invention. For example the spacing wedge can have an essentially straight form, as shown in the figures. Alternatively, the trailing spacing wedge can have along all or part, or portions of its length be bent, arch- shaped or of another for the purpose suitable form.

In the detailed description of the present invention, design details may have been omitted that are obvious for specialists in the field. Such obvious design details are included to the extent necessary in order to achieve a satisfactory function for the present invention. For example, components such as hydraulic hoses, connectors, fittings, and many more components that are essential for ensuring the proper function of the harvester head are included.

Even if certain preferred embodiments have been described in detail, variations and modifications within the scope of the invention can become apparent for specialists in the field of the invention and all such are regarded as falling within the scope of the following claims. For example, it is conceivable that the present invention consists of an accessory to existing harvester heads. This under the assumption that the harvester head design allows it.

It is conceivable that the harvester head has another for the purpose suitable design or configuration than that shown in the illustrated figures in this patent application. The harvester head may even consist of some in the future developed variant of a harvester head which is equipped with a spacing wedge in accordance with the invention concept of this patent application.

It is also conceivable that a spacing wedge in accordance with the present invention can be used in a double gripping harvester head unit. Further, it is also plausible that the present spacing wedge can be used in manually operated chain saws.

Advantages of the Invention

With the present harvester head and the methods for using the harvester head, the risk for stress cracks occurring during the cutting process will be to a significant extent reduced. A harvester head equipped with a spacing wedge in accordance with the present invention will minimize the risk of getting the chain saw bar stuck in the saw notch.

Claims

1. Harvester head (1) for felling and cutting elongated tree trunks (2) including at least one frame (6) fitted with at least one gripping device (9) and at least one feeder device (15) and one cutting device (18) with a chain saw bar (20) that is rotatable around a first swing axel (22) characterized by that the harvester head (1) includes at least one, after the cutting device (18), trailing spacing wedge (23) which is maneuvered forwards and backwards into the saw notch in a motion that is relative to the cutting device (18) and essentially perpendicular with the harvester head's and tree trunk's central axis intended to hinder pinching of the chain saw bar (20) and minimize stress cracks in the cut logs.

2. Harvester head (1) in accordance with claim 1 characterized by that the trailing spacing wedge (23) is arranged to pivot (rotate) in the radial direction in relation to the harvester head's (1) axial direction (that it during sawing essentially follows the chain saw bars movements).

3. Harvester head (1) in accordance with claim 2 characterized by that the trailing spacing wedge's rotational axis (fulcrum) and the chain saw bar's rotational axis (fulcrum) coincide or essentially coincide.

4. Harvester head (1) in accordance with one or more of the previous claims

characterized by that the trailing spacing wedge's (23) cross-section is L-shaped.

5. Harvester head (1) in accordance with one or more of the previous claims

characterized by that the trailing spacing wedge (23) is spring loaded.

6. Harvester head (1) in accordance with one or more of the previous claims

characterized by that the trailing spacing wedge (23) is attached to the harvester head (1) with at least one slip clutch.

7. Method for felling and cutting essentially elongated objects such as tree trunks with a harvester head in accordance with one or more of claims 1-6 characterized by that the harvester head is guided against a tree trunk and grips it where upon the rooted standing tree trunk is separated from its root section and then essentially positioned horizontally during de-branching and then moved in the horizontal direction in relation to the harvester head until an appropriate length is reached where upon the tree trunk is cut using a chain saw bar that penetrates into the tree trunk and that at least one trailing spacing wedge is completely or partially inserted into the saw notch after the chain saw bar in order to prevent the chain saw bar from getting stuck (pinched) in the saw notch and also to prevent the occurrence of stress cracks in the sawed log and that the chain saw bar and spacing wedge return to their original position after the cutting process is complete and are then ready to repeat this or another procedure.