The present invention is concerned with a device for splitting and chopping of wood, in parti- cular slender trees, to firewood or "chunks".

From the Finnish Patent Application No. 810,094, a device is previously known for the said purpose, which device, at the same time as it chops a piece of a certain length out of a tree fed into the device, splits this piece into two parts.

An essential component of the prior-art device is a large-diameter blade disc revolving on a central shaft, which disc is provided with a large opening. The counter-edge of the opening forms the blade chopping the tree. The chopping blade is jointly operative with a substantially V-shaped counter- blade constituting an extension of the bottom of the feed trough. Onto the blade disc, a wedge-shaped splitting blade has also been installed, which runs somewhat ahead of the chopping blade. Thereby, the splitting blade first splits the end of the tree fed into the cutting' opening, whereupon the following chopping-blade edge cuts a piece of a length corres¬ ponding to the feed-in length of the log out of the split end of the log.

It is an essential drawback of the device concerned that it is not self-feeding, but the operator of the machine must feed the tree one length of a chunk at a time throughout the entire splitting and chopping process. The said drawback may be considered highly important in view of the output and the ease of ope¬ ration of the machine.

It has been possible to solve this feeding problem by means of the device in accordance with the present invention, in which a log or tree once fed into the device is fed by the effect of the cutting process forcibly through the device and is chopped

and split to firewood of desired length.

The device in accordance with the invention consists of a driven shaft journalled as supported on an appropriate frame construction, of a blade disc mounted on the shaft perpendicularly, of blades mounted on the blade disc, as well as of a feed trough or equivalent for feeding the trees towards the blade disc, the final end of the trough at the same time functioning as a splitting and chopping counter-blade of the device. It is characteristic of the device that the cutting blades, projecting from the blade disc substantially perpendicularly, form at least one continuous spiral, extending over the distance of at least one revolution of the blade disc, at each side of the blade disc, the cutting edges of the said blade spirals becoming more distant from the plane of the blade disc while substantially following a screw line as the spiral approaches the centre of the disc from the circumference of the blade disc. The invention will be described in more detail with the aid of the attached exemplifying drawing of principle, which shows a preferred embodiment of the invention. In the drawing:

Figure 1 shows the blade disc with cutting blades, forming an essential component of the device in accordance with the invention, as seen from above in the direction of the plane of the blade disc, and

Figure 2 shows the blade disc with the blades as well as the final end of the feed trough as seen in the direction of the shaft of rotation of the device/

The shaft of rotation 1 of the device is journalled as revolving on an appropriate frame con¬ struction. A blade disc 2 is mounted on the shaft 1 perpendicularly and substantially centrally. In the embodiment shown, the blade disc carries one cutting blade 3, 3' on each of its sides. Each cutting blade projects from the blade disc substantially perpen-

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dicularly, i.e. as parallel to the shaft 1 of the device. Both of the blades constitute continuous cutting blades, which start at the circumference of the blade disc and approach the centre of the blade disc as spiral-shaped. At the same time, the cutting edge 3a and 3'a, respectively, of each blade becomes more distant from the face of the blade disc, substantially following a screw line. In the embodiment shown, each of the cutting-blade spirals 3, 3 ¹ , respectively, is placed on the blade disc so that they start from the circumference of the blade disc as shifted by half a revolution relative each other and extend on the blade disc over the distance of about one revolution. In the direction of the radius of the disc, the blades are placed at the distance of half the desired length of wood chunk from each other, but each of the blades approaches the centre of the blade disc from the circumference of the disc at the same spiral spacing equalling the length of wood chunk. The counter-blades of the blades 3, 3' supported on the blade disc consist of the terminal edges 5, 5' of the final end of the feed trough 4 in the device, against which edges the blades producing the chopping of the chunk of wood press each its half being split out of the tree. The counter-blade edges 5, 5' must be placed, in the way shown in Fig. 1, in V-shape as seen from above, wherein the depth of the V is at least equal to the distance of the ends of the blades 3, 3' in the direction of the diameter of the blade disc, and the opening of the shanks of the V is substantially the same as the maximum perpendicular distance of the blades 3, 3 * from the plane of the blade disc, of course in consideration of an appropriate cutting play. By means of the said blade arrangement, a scissor-type cutting process is guaranteed between the cutting blades and the counter-blades. At least the final part of the feed trough is made as of somewhat

curved or V-shaped section of the bottom portion so as to centre the tree or log to be split at the initial stage of the splitting in relation to the blade disc 2. A cross-sectional form approaching a semi-circular form is also possible, because the device is meant mainly for wood approximately smaller than a certain maximum diameter (about 300 mm) , because for heavier timber, there will also be more valuable use than burning. The inclination of the side walls of the bottom portion at the final end of the trough should be preferably chosen in consideration of the pitch angle of the screw line of the cutting blades 3, 3* so that the cutting edges 3a, 3'a of the cutting blades approach their counter- blade substantially perpendicularly, however, preferably so that the cutting blade and the counter-blade form an angle of a few degrees directed as downwardly inclined towards the middle portion of the bottom of the trough. In such a case the shear forces force the log to remain in position on the bottom of the trough. The circumference of the blade disc 2 follows the spiral form of the portions of the cutting blades that run nearest to the circumference, whereat a biting notch is formed at the initial point of each blade in the direction of rotation of the blade disc. As regards this notch, it is possible to shape the blade disc so that the joint between the cutting blade and the disc forms a wedge-shaped tip reaching forwards in the direction of rotation, which said tip strikes first against the middle of the tree to be split in a direc- tion substantially perpendicular to the longitudinal direction of- the tre . By means of this wedge pro- jection, the first splitting impact directed at the end of the log as well as the further splitting impact to be directed at the log in the subsequent cutting stages can be made efficient.

It is also possible to make the entire biting edge 2a on the blade disc as axe-shaped sharpened.

in particular in such embodiments in which the laterally projecting transverse cutting blades 3 and 3 ¹ do not start right from the said edge 2a.

The outer edge of the blade disc 2 may also be made sharpened, but this sharpening does not have a decisive significance, because the blades 3 and 3' pro¬ ducing the chopping-cutting, by means of their trans- verse shear force, tend to open the splitting-cut pro¬ duced by the ^" biting splitting edge 2a, in which case the splitting of the wood makes progress somewhat ahead of the blade disc, and the blade disc is unlikely to collide against the log with its circumferential edge.

After the biting edge 2a has split the end of the log at least up to its impact point, the blade 3 or 3' that is in cutting turn starts penetrating, by means of its cutting edge 3a or 3'a, respectively, into the split log half substantially perpendicularly to the fibre direction of the log and causes chopping-off of the split half, corresponding to its spiral-shaped curved track, against the counter-blade formed by the final end of the wall of the feed trough. In the embodiment shown, each blade is dimensioned so that the blades perform a full transverse, i.e. axial, cutting stroke during one full revolution .of the blade disc. With a blade arrangement of this type, when one of the blades comes halfway in cutting through the cross-section of its log half, the splitting edge 2a of the other blade strikes against the side of the log at a distance of half the length of a chunk of wood and goes on splitting the log. At the same time, the corres¬ ponding chopping blade starts its own cutting-off. As - the blades are, in the way shown, spiral-shaped and approach the centre of the blade disc, during its cutting each blade produces a corresponding feeding or pulling force on the log or tree to be chopped, whereat, during a full cutting movement of each blade, the log is pulled inwards over a distance corresponding to the

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radial distance between the initial end and the final end of the blade, i.e. to the desired length of the chunk of wood. By means of the phase shift of the blades shown in the drawing, it has been achieved additionally that this feeding effect goes on uninterrupted through¬ out the entire process of chopping of the log.

In order to eliminate any detrimental effects of the chopping forces acting upon the log in a way varying from side to side while the chopping goes on, which said forces may tend to shake the log in the lateral direction, it is also possible to accomplish the invention so that both chopping blades start at the same position on the circumference of the blade disc. In this solution it is justified to make the blades such that they extend somewhat longer than one revolution of the disc, in order that the new cutting could have started one length of a chunk further away before the preceding cutting is completed. In this way a continuous feed is ensured for the log when the blade spirals are in constant contact with the log. In the said latter- solution, the power requirement of the device may, however, vary to a higher extent than in the suggested former solution, in which the blades are phase-shifted in relation to each other. It is perfectly within the scope of the invention also to design the cutting blades at both sides of the blade disc as double spirals, in which case the blade spirals must be placed apart from each other in the radial direction of the disc in accordance with the length of the chunk of wood. In this embodi¬ ment, the starting points of the blades on the circum¬ ference of the disc should be preferably placed as spaced by 90°, whereby the cutting operations can be made to start smoothly. As further advantages of the positive feed achieved by means of the invention may be mentioned that the device may be provided with an appropriate lopping

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device, by means of which the branches can be removed from the trees to be chopped before chopping. The said equipment alternative is most advantageous in view of the overall working as regards the output. Further, it should be noticed that the device in accordance with the invention is,by its nature, fed from the side, whereat, e.g., installed at the rear of a tractor and driven by the tractor, it can be operated fluently, e.g., in forest conditions. The feed of the trees from the side permits the haulage of a trailer by the tractor in spite of the chopping device mounted on the tractor without any difficulty, or even impossibility, of the feeding of the trees into the chopping machine. In such a case, an appropriate elevator can be mounted at the side of the chopping machine to carry the chunks of wood immediately onto the connected trailer. If the device is additionally provided with the lopping device mentioned above, the working of the device in forest conditions can be made highly fluent. For example, trees felled for the purpose of thinning of the forest need not be transported anywhere from the forest, but they may be heaped into appropriate heaps alongside the chosen driving paths with the trees directed perpendi¬ cularly to the driving path. Thereby, the tractor with the said equipment may be driven along the driving path to alongside each heap of trees, from which the unlopped trees are pushed into the mouth of the chopper. A tree once fed in proceeds by the effect of the self-feed of the machine through the chopper and further, as appro- priate chunks of wood, carried by the elevator, onto the trailer. Working with the device in accordance with the invention is very speedy, because the person operating the machine may pick up the next tree from the heap of trees ready to the feeding position while the preceding tree is being bitten by the machine.