Felling unit for harvesting small dimensioned wood and a method for felling small dimensioned wood

Abstract

The invention concerns a felling unit (1) comprising: a main body (100) comprising a feeding system (200), a cutting system (300), and an intermittent storage (400). The feeding system (200) comprises at least a first rotating feeder (210) and a second rotating feeder (220) for feeding wood through the cutting system (300) and into the intermittent storage (400), the feeders (210; 220) each being rotationally actuated about respective rotation axes (xl; x2) with at least one actuator. The cutting system (300) comprises a first actuated cut element (310) and a second non-actuated cut element (320) arranged such that the movement of the first actuated cut element (310) drives the wood against the second non-actuated cut element (320). The intermittent storage (400) is arranged such that the feeding system (200) and the cutting system (300) feed the cut wood into the intermittent storage (400). The invention also relates to a method for continuous felling small dimensioned wood.

Description

[0001] FELLING UNIT FOR HARVESTING SMALL DIMENSIONED WOOD AND A METHOD FOR FELLING SMALL DIMENSIONED WOOD

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a felling unit intended for cutting and harvesting small dimensioned wood and to a method for felling small dimensioned wood.

[0004] BACKGROUND OF THE INVENTION

[0005] Great amount of renewable energy is left unutilized in forests all around the world as small dimensioned wood, sometimes also referred to as energy wood, is difficult, slow, inefficient, and not cost-effective to fell and harvest with the current commercially available machinery on the market. Small dimensioned wood refers to wood which does not qualify as timber and includes for example smalldiameter wood from thinning or small dimensioned wood being harvested from seedling stands and young forests. Further, to be able to ensure favourable growth conditions for logs, small-dimensioned wood must be removed from forests in connection with forest management. Young forests wherein said small dimensioned wood is not actively managed also pose a serious threat of wildfires during droughts, thus in turn potentially affecting the environment and the climate negatively. Therefore, there is an imperative need for working and efficient solutions for managing the small dimensioned wood such that the energy stored therein can be utilized economically while the environmental risks are simultaneously managed.

[0006] The traditional harvesting heads aimed at harvesting large trees are mainly used for single-tree processing and cannot be as such efficiently used for the purpose of managing the young forests having small dimensioned wood. The working principle of the traditional harvesters is generally to grab the tree with a claw grip, and then to fell it with reciprocating motion either with sawing, pinching, or guillotine tools. Both of these felling operations for large trees require high power machinery and large units which are difficult to operate in challenging terrain and tight spaces. Further, the single-tree processing of traditional harvesting heads causes high number of interruptions during harvesting and thus is highly inefficient in harvesting of small dimensioned wood where the quantity of the trees is significantly higher than when larger trees are harvested.

[0007] These issues have been attempted to be solved previously, and there are also known felling units intended for harvesting small dimensioned wood in particular. These known solutions utilize two continuously actuated circular saws or crushers that are driven in opposite directions in order to pass the wood through the cutting system. Use of two continuously actuated cutting elements requires more maintenance and introduces unnecessary weight to the felling unit. Further, in the known solutions the cutting systems utilize very dull saws or crushers to fell the trees by forcing the trees between the two actuated saws or crushers transferring a great deal of the forces to the axes they are connected to. So, such felling translates to high forces acting on the cutting system and the felling unit as whole and requires high power from the machinery. This in turn requires the machinery, the power sources, and the operating system to be dimensioned to handle such forces without breaking and results in overall heavier, more robust, and unnecessarily high-powered felling units that are not cost effective to produce or utilize.

[0008] Therefore, there exists a clear need for an improved felling unit that can be used in mechanically performed young forest management to reduce the risk of forest fires more economically and to alleviate the above outlined issues in current felling units.

[0009] BRIEF DESCRIPTION OF THE INVENTION

[0010] An object of the present invention is to provide a felling unit so as to alleviate the above disadvantages and to provide a felling unit with improved felling characteristics. The objects of the invention are achieved by a felling unit which is characterized by what is stated in the independent claim. The preferred embodiments of the invention are disclosed in the dependent claims.

[0011] The invention is based on the idea of providing the felling unit with an improved cutting system comprising a first actuated cut element and a second nonactuated cut element acting as a counter blade adapted to co-operate with aid of a feeding system to better cut small dimensioned wood. This way, the felling unit is more reliable, provides a cleaner cut on the wood, and can be implemented with a lighter construction, thus improving overall efficiency of the harvesting operation.

[0012] It has been noted in praxis that by performing the felling with the felling unit according to the invention, cleaner cuts can be performed on the small dimensioned wood, instead of crushing the wood, which decreases the power and forces required to perform the cutting operation. This in turn allows the structure of the felling unit and the power sources to be better optimized for the felling operation and both fuel use, initial costs, running costs, and operating costs can be reduced compared to the solutions present in the market. Further, the felling unit of the invention better enables mechanical maintenance performed with machinery on young forests, thus directly providing a solution for decreasing the chances of wildfires that are caused by lack of maintenance while simultaneously obtaining economic benefits.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which figure 1 shows an elevated perspective view of a felling unit according to an embodiment of the invention; figure 2 shows a lower perspective view of the felling unit of figure 1 wherein particularly the cutting system of the felling unit can be seen from below; figure 3 shows a front view of the felling unit of figure 1; figure 4 shows a bottom view of the felling unit of figure 1; figure 5 shows a flow chart of an example method for continuous felling of small dimensioned wood; and figure 6 shows an elevated view of a felling unit according to a second embodiment of the invention in open position; figure 7 shows an elevated view of the felling unit of figure 6 in closed position; figure 8 shows a bottom view of the felling unit of figure 6 in open position; and figure 9 shows a bottom view of the felling unit of figure 6 in closed position.

[0015] DESCRIPTION OF AT LEAST ONE EMBODIMENT

[0016] The felling unit 1 according to the invention for harvesting small-dimensioned wood is intended to be coupled to a movable working machine. The working machine may be wheeled or tracked. The felling unit 1 is preferably fitted to a boom of a movable work machine, such as a forest tractor or a harvester to allow for better control of the position and tilting of the felling unit. Alternatively, the felling unit 1 may also be directly coupled to a movable working machine without the use of a boom, for example by replacing the bucket in a wheel loader with the felling unit 1. In such configuration the position of the felling unit is mainly controlled with the movement of the working machine itself. The felling unit is preferably coupled to the working machine through a tilting element, which allows the felling unit 1 to be tilted and rotated in necessary directions to improve control and usability of the felling unit 1.

[0017] Figure 1 shows a felling unit 1 comprising a main body 100 comprising a feeding system 200, a cutting system 300, and an intermittent storage 400. This configuration allows a batch process for harvesting small dimensioned wood. The cutting system 300 allows plurality of wood to be cut simultaneously or continuously, while the feeding system 200 feeds the wood into the intermittent storage 400 wherein a predetermined amount of wood can be stored depending on the sizing of the intermittent storage. By storing the wood into the intermittent storage 400, the wood is bunched by the felling unit 1 and can be thus efficiently handled once the felling operation is interrupted. The bunched wood can then be emptied from the intermittent storage 400 as a pile, and thus the wood can be easily collected. Based on the sizing of the intermittent storage 400 the harvesting operation can be continuously performed for significant time periods before the intermittent storage 400 must be emptied, thus resulting in efficient felling operation.

[0018] The feeding system 200 comprises at least a first rotating feeder 210 and a second rotating feeder 220 feeding wood into and through the cutting system 300 and further after cutting into the intermittent storage 400. This allows the operator to only bring the felling unit 1 into vicinity of the tree, and the feeding system 200 automatically and continuously guides the trees into the felling unit 1 to a correct position for felling, thus improving user friendliness of the felling unit by reducing the accuracy demands. The feeders 210; 220 are each being rotationally actuated about respective rotation axes xl; x2 with at least one actuator. The rotation directions of the rotation axes xl;x2 are opposite one another, such that the rotation feeds the wood between the rotation axes xl;x2.

[0019] The cutting system 300 comprises a first actuated cut element 310 and a second non-actuated cut element 320 arranged such that the movement of the first actuated cut element 310 drives the wood against the second non-actuated cut element 320. The rotation direction of the first actuated cut element 310 is the same as the rotation direction of the first feeder 210, thus driving together in cooperation the wood against the second non-actuated cut element 320 acting as a counter blade. This is a simple to manufacture, cost effective, and light weight solution for improving the cutting properties of the cutting system 300. The counter blade particularly provides a cutting or a slicing action on the wood compared to the sawing or grinding action asserted by the first actuated cut element 310, thus resulting in a cleaner cut and less forces acting on the felling unit 1. Small dimensioned wood can be more easily sliced than large trees. Use of non-actuated counter blade also simplifies the maintenance of the felling unit 1 by utilizing fewer moving parts. A further advantage of the second non-actuated cut element 320 is that it bears the load of the wood during felling and before the wood is fed into the intermittent storage. This is particularly advantageous compared to previous solutions where two actuated cut elements are used. Load on the rim of an actuated cutting element exerts downward forces on the rim, thus possibly even tilting the actuated cut element increasing friction and power losses, resulting in damages, faster deterioration of the cut element, or power leaks in the felling operation.

[0020] The intermittent storage 400 is arranged such that the feeding system 200 and the cutting system 300 feed in co-operation the cut wood into the intermittent storage 400. In other words, the intermittent storage is arranged behind the cutting system 300 and the feeding system 200 in feeding direction F of the felling unit 1. This allows the wood to be automatically bunched and collected to the intermittent storage simply by powering the feeding and the cutting systems 200; 300. This gathering of the cut wood facilitates continuous felling of small dimensioned wood, and allows for faster felling and harvesting, making it more economically viable.

[0021] In the embodiment of figure 1, the first actuated cut element 310 and the second non-actuated cut element 320 are arranged offset in the axial direction x. This allows the cut elements 310; 320 to be positioned such that they may overlap, and the contours of each cut element can be better designed to improve the cooperation between the cut elements, resulting in improved cutting action. Particularly, in the embodiment of figure 1 the second non-actuated cut element 320 is positioned above the first actuated cut element 310. This configuration provides the advantage that the first actuated cut element 310 drives the wood below the second non-actuated cut element 320 while the feeding system 200 drives wood above the second cut element 320, thus improving the balance of the driving forces on the wood resulting in a cleaner cut, and decreasing possibilities of the wood leaning or tilting during the cutting process. Alternatively, the second non-actuated cut element 320 could be also positioned below the first actuated cut element to ensure that the wood cut by the first actuated cut element 310 is easier deposited into the intermittent storage 400.

[0022] In the embodiment of figure 1, the first actuated cut element 310 and the second non-actuated cut element 320 overlap each other when viewed from above or below, as can be seen in figure 2, for instance. In the embodiment of figure 1, the overlapping is arranged such that the second cut element 320 extends above the first actuated cut element 310 and covers it at least partially. This allows the entire cutting section to be covered by a cutting element 310;320 in order to ensure that the wood is completely cut. This facilitates operation and efficiency of the felling unit 1 as stuck situations resulting from wood not being entirely cut before attempting to insert it into the intermittent storage 400 can be avoided, and thus downtime of the felling unit 1 can be decreased. Alternatively, the second cut element 320 may also extend below the first actuated cut element 310.

[0023] In the embodiment of figure 1, a cutting edge 321 of the second nonactuated cut element 320 is arranged angled towards the intermittent storage 400 relative to a feeding direction F defined by the feeding system 200. The feeding direction F is perpendicular to the rotation axes xl;x2 and determined by the co-operation of the rotation of the axes xl;x2. The second non-actuated cut element 320 being angled facilitates cutting and slicing of the wood and reduces impacts caused by the wood coming in contact with the second non-actuated cut element 320. The cutting edge is particularly angled towards the intermittent storage 400 which in turn further facilitates guiding the wood into the intermittent storage 400. The cutting edge 321 is preferably angled on a cutting plane set by the first actuated cut element 310 and the second non-actuated cut element 320.

[0024] Preferably, the cutting edge 321 of the second non-actuated cut element 320 comprises a straight edge, and / or a curved concave edge, and / or a curved convex edge. In the embodiment of figure 1, the second non-actuated cut element 320 comprises a combination of a straight edge and a curved concave edge. Particularly, the cutting edge 321 is divided into two sections where a first edge section 321a comprises a straight edge and the second edge section 321b comprises a curved edge. In this configuration the first edge section 321a is closer to the second rotation axis x2 which pushes the wood along this straight edge. The second edge section 321b is closer to the first rotation axis xl which pushes the wood against this concave curved edge, where this curvature allows the wood to glide on the edge instead of colliding against it straight on, thus facilitating the cutting properties of the cutting system 300.

[0025] In the embodiment of figure 1, the second non-actuated cut element 320 is rigidly mounted on the main body 100 with bolts. However, any suitable way of mounting the non-actuated cut element 320 can be used. Detachable mounting elements such as bolts are preferred, as it allows the second non-actuated cut element 320 to be replaced if damaged or dulled. Alternatively, the second nonactuated cut element 320 can also be integrally formed in the main body 100.

[0026] In an embodiment not illustrated, the second non-actuated cut element 320 is suspension mounted on the main body 100 such that the second non-actu- ated cut element 320 may yield. This is particularly useful in situations wherein the wood is jammed or stuck against the second non-actuated cut element 320 and forcing the wood further against the second non-actuated cut element 320 would cause high force peaks on the felling unit. With aid of suspension, these spikes in forces can be alleviated and the peaks can be lowered. By yielding with the force, and with aid of the feeding system 200 and the first actuated cut element 310, the cutting of the wood is improved and possible damages to the felling unit 1 can be avoided. The suspension can be implemented for example with traditional springs, adjustable hydraulic springs, or adjustable pneumatic springs, for instance. After the yielding, the suspension returns the second non-actuated cut element 320 back to its original position.

[0027] In an embodiment not illustrated, the second non-actuated cut element 320 is circular and bearing mounted on the main body 100 such that the second non-actuated cut element 320 is able to freely rotate. This bearing mounting can be implemented on the same rotation axis x2 as the second feeder 220, such that the rotation of the axis x2 is not conveyed to the second non-actuated cut element 320. Alternatively, the non-actuated cut element 320 can also be bearing mounted on a parallel non-concentric axis, or a separate concentric axis in order to avoid possible forces of the rotating axis x2 affecting the non-actuated cut element 320 during cutting when wood exerts pressure on it. Alternatively, the second non-actuated cut element 320 may also be elliptical and bearing mounted on the main body 100 such that the elliptical cut element is able to rotate about a rotation axis. The elliptical profile of the cut element introduces a varying cutting surface during the felling operation, which at some points may yield from the wood while simultaneously introducing increased cutting forces elsewhere on the wood. This elliptical bearing mounted cut element can be paired with the suspension mounting mentioned before.

[0028] Preferably, the first actuated cut element 310 comprises a round saw blade or an elliptical saw blade, particularly a toothed round saw blade or a toothed elliptical saw blade. Even more preferably, the first actuated cut element 310 comprises a chain saw blade. Both of these are readily available sawing solutions that can be obtained on the market. A particularly well working chain saw blade is described in more detail in patent publication US57656004A, for instance.

[0029] In the embodiment of figure 1, a first actuator actuates the rotation of the first feeder 210 and the first actuated cut element 310, and a second actuator actuates the rotation of the second feeder 220. In this case the first actuated cut element 310 and the first feeder 210 are arranged on the same axis xl that drives the rotation of both of these elements. This allows that the first actuator can be dimensioned to be more powerful than the second actuator, as the first motor practically powers the cutting action and half of the feeding, while the second actuator is only involved in feeding. The rotating motion of the rotating axes xl;x2 can be actuated with actuators by use of direct drive or power transmission elements for transmitting the motion of the actuators into rotating motion of the axes xl;x2. Such transmission elements are chains or power transmission belts, for example.

[0030] Alternatively, the first actuated cut element 310 and the first feeder 210 can be separately actuated with separate actuators and thus be arranged on separate axes. The felling unit 1 may also comprise gearing in order to alter the gear ratios of the first cut element 310 compared to the first feeder 210 in order to obtain different rotation speeds while utilizing the same actuator.

[0031] Preferably, the at least one actuator is a hydraulic motor, a pneumatic motor, or an electric motor. Hydraulic motor is particularly preferable, as hydraulic power needed for the hydraulic motor is typically well available in the booms of work machines, and the hydraulic motor is also an efficient, durable and maintenance-free actuator.

[0032] In the embodiment of figure 1, the first feeder 210 and the second feeder 220 each comprise a plurality of feeding flaps 211; 221 for feeding the wood into the felling unit 1. Said embodiment comprises 4 feeding flaps 211; 221, which is the most preferable configuration, where the feeding flaps 211; 221 are evenly spaced on each feeder 210; 220 such that the angle between each feeding flap 211; 221 is substantially 90 degrees. Also, other quantities of feeding flaps 211; 221 can be used, preferably 3 to 8 feeding flaps 211; 221. However, the disadvantage with too high quantity of feeding flaps 211; 221 is that the feeding flaps 211; 221 may interfere with larger pieces of wood, thus negatively affecting the performance of the felling unit 1. Similarly, the disadvantage with not enough feeding flaps 211; 221 is that the feeding volume slows down with same rotation speed, and same feeding frequency is not obtained.

[0033] Preferably, the feeding flaps 211; 221 extend in axial direction of the rotation axes xl; x2 for at least 50% of the axes xl; x2. This facilitates feeding the wood in upright position and not allowing the wood to tilt or fall during feeding, which could cause operational issues such as jamming or clogging of the felling unit 1.

[0034] Preferably, the feeding flaps 211; 221 are preferably elastic and durable material such as natural rubber, for instance. Also, other suitable materials may be used which provide suitable strength and flexibility profiles to be able to perform properly.

[0035] Preferably, the feeding flaps 211; 221 comprise a substantially rectangular profile and / or extend continuously along the rotation axes xl; x2.

[0036] In the embodiment of figure 1, the rotation axis xl of the first feeder 210 and the rotation axis x2 of the second feeder 220 are parallel and are spaced apart such that an opening 0 is formed between the rotation axes xl; x2 for feeding the wood into the intermittent storage 400, and the feeding flaps 211; 221 are dimensioned such that the length 11 & 12 of the feeding flaps 211; 221 are at least 50% of the width of the opening 0. This ensures that the feeders 210; 220 are able to maintain contact with the wood during the entire cutting process, and both the feeding and cutting operations are better supported.

[0037] In the embodiment of figure 1, the rotation speed of the first axis xl and the second axis x2 are the same, and the rotation phases of each feeder 210; 220 are offset related to each other such that the feeding flaps 211 of the first feeder 210 do not collide with the feeding flaps 221 of the second feeder 220. This allows the feeding flaps 211;221 having above-described dimensions to be used without the feeding flaps 211; 221 interfering with operation of one another.

[0038] In the embodiment of figure 1, the rotation of the rotation axes xl;x2 can be reversed and be rotated in a second direction opposite the first direction. By reversing the rotation, the feeders 210;220 can be used to mechanically empty the intermittent storage 400. This helps to minimize the unloading time and does not require outside tools for the emptying. The felling unit 1 can also be simultaneously tilted downward, such that the feeding direction F is away from the ground, meaning that the unloading direction is towards the ground, and the unloading is facilitated with gravity.

[0039] In an embodiment not illustrated, the felling unit 1 further comprises an a third actuated cut element below the second non-actuated cut element 320. Preferably, said third actuated cut element may be formed as an elongated chain saw blade. The position of the third actuated cut element can be altered by rotating it about a rotation axis located on a first end of the third actuated cut element. In that instance a cutting portion of the third actuated cut element is located on a second end opposite the first end. Alternatively, the position of the third actuated cut element can be altered by moving it linearly. In both cases the movement of the third actuated cut element can be actuated with a separate actuator, such as a hydraulic or pneumatic cylinder. Further, in both cases the actual cutting motion is preferably performed with a chain saw blade powered by a separate actuator, for example a hydraulic motor or an electric motor. This allows much higher speeds to be used in the third actuated cut element, which in turn supports the felling of the felling unit 1. Such cut elements themselves are known per se from different applications in traditional harvester heads. Preferably, the third actuated cut element covers more than 25% of the opening 0 between the rotation axes xl;x2. Even more preferably the third actuated cut element covers 50% of the opening 0 between the rotation axes xl; x2.

[0040] Figure 5 illustrates a flow chart of an embodiment of a felling method for felling small dimensioned wood. This method may be implemented for felling small dimensioned wood with the felling unit 1 illustrated in figures 1 to 4. The embodiment comprises steps of A providing a suitable felling unit 1, preferably as described before in this description; B feeding small dimensioned wood into the cutting system 300 by bringing the felling unit 1 in contact with the wood, C felling the wood by driving the wood against the second non-actuated cut element 320 by use of the feeding system 200 and the first actuated cut element 310, and finally D storing D the wood temporarily in an intermittent storage 400.

[0041] Preferably, the felling unit is a felling unit particularly intended for harvesting small dimensioned wood.

[0042] Figures 6 to 9 illustrate a second embodiment of the felling unit 1 further comprising a third actuated cut element 330 arranged as a pivoting blade pivoting about the rotation axis xl. The third actuated cut element 330 is arranged coaxial but rotationally independent from the first actuated cut element 310 on the rotation axis xl. This third actuated cut element 330 is intended to provide means for felling larger dimensioned wood during the felling operation, thus allowing also such trees to be felled more efficiently with the same felling unit 1, reducing the need for further felling machinery in woods consisting of mainly small dimensioned wood. Larger dimensioned wood in this context meaning trees having a diameter larger than 10 cm, for instance.

[0043] The third actuated cut element 330 can be rotated to an open position as shown in figures 6 and 8, where the third actuated cut element 330 is pivoted away from the second non-actuated cut element 320. In this open position, the third actuated cut element 330 does not interfere with the operation of the first actuated cut element 310 and the feeders 210;220 when felling small dimensioned wood. In this embodiment, as seen from figure 6, the open position is about 45 degrees open from the feeding direction, allowing it to function also as a funnel towards the first actuated cut element 310 and the second non-actuated cut element 320, thus guiding the small dimensioned wood towards the cutting system. Preferably but not limited to, the open position is within 15 to 70 degrees open related to the feeding direction. When the third actuated cut element 330 is angled open in relation to the feeding direction, it aids with funnelling. When the third actuated cut element 330 is dimensioned accordingly lengthwise, in this open position the third actuated cut element 330 does not protrude outside of the felling unit’s side walls, which could hinder the felling units 1 operation and manoeuvrability.

[0044] When the felling unit 1 is brought into contact with a larger dimensioned wood, the third actuated cut element 330 can be rotated to a closed position as shown in figures 7 and 9, where the third actuated cut element 330 is positioned against the second non-actuated cut element 320, closing entirely a distance between the cut elements 330;320. When the distance is entirely closed, the wood is forced to a cut. While the third actuated cut element 330 is actuated, the first actuated cut element 310 and the feeders 210;220 may be completely still, operating at lower rotation speed, or be rotating normally to pull the wood closer into the felling unit 1, and thus aiding with the positioning of the wood to be cut.

[0045] In this second embodiment, the third actuated cut element 330 is powered separately from the first actuated cut element 310 and the feeders 210:220 allowing it to be operated entirely independently, and the actuation can be triggered manually by the user. This way, the third actuated cut element 330 can also be used to aid the cutting system 300 while felling smaller dimensioned wood if any stuck situations occur where the cutting system 300 is not able to cut the wood entirely for any reason.

[0046] Preferably, the third actuated cut element 330 is dimensioned such that in the closed position a cutting edge 331 of the third actuated cut element 330 comes into contact with a corresponding cutting edge 323 of the second non-actuated cut element 320. Further, the cutting edges 331;323 have a similar outline in order to entirely close the distance between the third actuated cut element 330, and the second non-actuated cut element, forcing the cut elements 330;320 to cut the wood entirely. In this case both cutting edges 331; 323 are straight, but also other suitable corresponding cutting edge outlines can be implemented.

[0047] Preferably, after the larger dimensioned wood has been cut, the feeders 210;220 are rotated in the feeding direction to push the wood into the intermittent storage. Alternatively, if the larger dimensioned wood is too large for the intermittent storage, the feeders 210;220 can be rotated in the second direction to push the wood away from the felling unit 1, and the third actuated cut element 330 is rotated in a second direction to move it to open position to either repeat a cut on another larger dimensioned wood, or to continue felling the smaller dimensioned wood.

[0048] In the embodiment of figures 6 to 9, the third actuated cut element 330 is rigid, and further consist of an arm, preferably curved, extending radially from the rotation axis xl, and a straight blade connected to the arm. This allows the blade to be easily changed and replaced in the arm during maintenance. Alternatively, the third actuated cut element 330 could be formed as one piece element connected to the rotation axis.

[0049] In the embodiment of figures 6 to 9, the third actuated cut element 330 is positioned on a same horizontal plane as the second non-actuated cut element 320, allowing the cutting edges to come to contact in a pinching motion in the same plane. So in this configuration, the third actuated cut element 330 is positioned above the first actuated cut element 310 and below the first feeder 210 on the rotation axis xl. Alternatively, the third actuated cut element 330 could be provided vertically offset to the second non-actuated cut element 320 to work as by-pass- blades, for example above or below the second non-actuated cut element 320.

[0050] In an embodiment not illustrated, the third actuated cut element 330 is a folding blade. Meaning that the third actuated cut element comprises at least two hinged sections, such that the cut element is allowed to fold in a direction where the blade faces. In this configuration the third actuated cut element 330 comprises a straight position and a folded position, which define end ranges of the folding blade. The third actuated cut element 330 preferably further comprises a return spring for returning the third actuated cut element to the straight position when no outside forces are exerted on the third actuated cut element 330.

[0051] During cut operation of the folding blade, the blade remains in the straight position as the third actuated cut element 330 is actuated in the first direction, meaning the cutting direction. However, after the cut has been performed, the hinged configuration allows the third actuated cut element 330 to fold when actuating in the second direction, allowing it to move out of the way of the incoming wood during felling operation. The folding is done by the incoming wood exerting forces in the feed direction, while the third actuated cut element 330 is moving against the feed direction. This improves the operation of the felling unit, as felling can be continued while retracting the third actuated cut element 330.

[0052] In an embodiment not illustrated, the third actuated cut element 330 is comprised of two cut elements on parallel planes perpendicular to axis xl, the two cut elements positioned vertically apart. This way one of the cut elements can be positioned above the second non-actuated cut element 320, and the other can be positioned below the second non-actuated cut element 320. This balances the cutting forces to be symmetrical in respect to the second non-actuated cut element 320, and reduces tilting forces on the wood being cut. Further, the two cut elements can be rotationally staggered, meaning that the relative rotation position of the cut elements is offset. This allows one of the cut elements to come into contact with the wood before the other, which can in some instances improve the cut.

[0053] In another embodiment not illustrated, the third actuated cut element 330 is arranged on a further rotation axis instead of being coaxial with the rotation axis xl. Positioning the third actuated cut element 330 coaxial with the rotation axis xl is not essential, as long as the positioning allows both the first actuated cut element 310 and the first feeder 210 to operate, and the third actuated cut element 330 to operate without collisions.

[0054] It will be obvious to a person skilled in the art that the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

CLAIMS1. A felling unit (1) comprising: a main body (100) comprising a feeding system (200), a cutting system (300), and an intermittent storage (400); wherein the feeding system (200) comprises at least a first rotating feeder (210) and a second rotating feeder (220) for feeding wood through the cutting system (300) and into the intermittent storage (400), the feeders (210; 220) each being rotationally actuated about respective rotation axes (xl; x2) with at least one actuator; the cutting system (300) comprises a first actuated cut element (310) and a second non-actuated cut element (320) arranged such that the movement of the first actuated cut element (310) drives the wood against the second non-actu- ated cut element (320); and the intermittent storage (400) is arranged such that the feeding system (200) and the cutting system (300) feed the cut wood into the intermittent storage (400).

2. The felling unit (1) according to claim 1, wherein the first actuated cut element (310) and the second non-actuated cut element (320) are arranged offset in the axial direction (x), preferably such that the second non-actuated cut element (320) is positioned above the first actuated cut element (310).

3. The felling unit (1) according to claim 2, wherein the first actuated cut element (310) and the second non-actuated cut element (320) overlap, such that the second non-actuated cut element (320) extends above the first actuated cut element (310) and covers it at least partially.

4. The felling unit (1) according to any of the preceding claims 1 to 3, wherein the second non-actuated cut element (320) is suspension mounted on the main body (100) such that the second non-actuated cut element (320) may yield.

5. The felling unit (1) according to any of the preceding claims 1 to 3, wherein the second non-actuated cut element (320) is rigidly mounted on the main body (100) or integrally formed on the main body (100).

6. The felling unit (1) according to any of the preceding claims 1 to 5,wherein a cutting edge (321) of the second non-actuated cut element is arranged angled towards the intermittent storage (400) relative to a feeding direction (F) defined by the feeding system (200).

7. The felling unit (1) according to any of the preceding claims, wherein the cutting edge (321) of the second non-actuated cut element (320) comprises a straight edge, and / or a curved concave edge, and / or a curved convex edge.

8. The felling unit (1) according to any of the preceding claims, wherein the cutting edge (321) of the second non actuated cut element (320) comprises a first edge section (321a) and a second edge section (321b), wherein the first edge section (321a) comprises a straight edge and the second edge section (321b) comprises a curved edge.

9. The felling unit (1) according to claim 1, wherein the second non-actuated cut element (320) is circular and bearing mounted on the main body such that the second non-actuated cut element (320) is able to freely rotate.

10. The felling unit (1) according to any of the preceding claims, wherein the felling unit (1) further comprises a third actuated cut element (330) arranged as a pivoting blade on the rotation axis (xl), the third actuated cut element (330) being co-axial but independently rotatable from the first actuated cut element (310) or the first rotating feeder (210).

11. The felling unit (1) according to claim 10, wherein the third actuated cut element (330) comprises an open position where the third actuated cut element (330) is positioned at a distance from the second non-actuated cut element (320), such that it does not interfere with the operation of the first actuated cut element (310) and the second non-actuated cut element (320).

12. The felling unit (1) according to claims 10 or 11, wherein the third actuated cut element (330) is a folding blade comprising at least two hinged sections, the hinge allowing the hinged section to fold in a direction the blade faces, and wherein the third actuated cut element (330) has a straight position and a folded position defining end ranges of the hinge.

13. The felling unit (1) according to any of the preceding claims, wherein the rotation axis (xl) of the first feeder (210) and the rotation axis (x2) of the second feeder (220) are parallel and are spaced apart such that there is an opening (0) between the rotation axes (xl; x2) for feeding the wood into the intermittent storage, and the feeding flaps (211; 221) are dimensioned such that the length (11 & 12) of the feeding flaps (211; 221) are at least 50% of the width of the opening CO).

14. The felling unit (1) according to claim 13, wherein the rotation speed of the first axis (xl) and the second axis (x2) are the same, and the rotation phases of each feeder (210; 220) are offset related to each other such that the feeding flaps (211) of the first feeder (210) do not collide with the feeding flaps (221) of the second feeder (220).

15. The felling unit (1) according to any of the preceding claims, wherein the felling unit (1) is a felling unit (1) for harvesting small dimensioned wood.

16. A felling method for continuous felling small dimensioned wood, the method comprising: providing (A) a felling unit 1 according to claim 1, feeding (B) small dimensioned wood into the cutting system (300) by bringing the felling unit 1 in contact with the wood, felling (C) the wood by driving the wood against the second non-actu- ated cut element (320) by use of the feeding system (200) and the first actuated cut element (310), storing (D) the wood temporarily in an intermittent storage (400).

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