The invention relates to a method according to the preamble of the appended claim 1 for making firewood with a wood chopping machine. The invention also relates to a wood chopping machine according to the preamble of claim 2.

Wood chopping machines of prior art which are available for making firewood (for example, wood chopping machines manufactured and marketed by the applicant) normally comprise a feeding device, a cross- cutting device, and a hydraulically driven splitting device, in which a log of a fixed length cross-cut from a tree trunk is split by pushing it against a latticed splitting blade by means of the moving end of a hydraulic cylinder. Normally, the feeding device is a conveyor belt and the cross-cutting device is a circular saw or a chain saw. The length of the log to be cross-cut from a trunk is normally determined by means of a mechanical stop, which is hit by the trunk after the length of the log to be cross-cut from the trunk has moved past the sawing line of the cross-cutting device. In the most conventional wood chopping machines, the conveyor belt is stopped when the trunk hits the stop, after which the cross-cutting device is started and the trunk is crosscut. Normally, the sawing movement is implemented manually, for example by means of a turning handle movable in the vertical direction. This turning of the handle to the upper position will start the conveyor belt and will stop it when the sawing movement has been started after the turning handle has been returned slightly downwards. After the cross-cutting, the log cut off the trunk lying on the feeding machine will normally drop into a splitting chute of the splitting device placed on a lower level and after the conveyor belt. After this, the splitting head at the end of the movable end of the splitting cylinder of the splitting device is moved by the splitting cylinder so that it pushes the log against the splitting blade at the other end of the splitting chute, wherein the log is split into billets. When the turning handle that turns the saw is turned back to the upper position, the feeding device is re-started, wherein the trunk moves again forward by the length of one log so that a new log will be ready for cross-cutting. At present, wood chopping machines are also known, in which the different steps of wood chopping are, in part or in whole, automatically controlled. In recent years, in wood chopping machines of the above-described kind, i.a. the adjustment of the length of the stroke of the splitting cylinder has been developed so that the length of the stroke is adjusted according to the length of the log to be split. In this way, it has been possible to increase the speed of the work movement of the splitting device and thereby the productivity of the whole wood chopping machine.

A wood chopping machine in which the length of the stroke of the splitting cylinder is adjusted according to the length of the log to be cut off the trunk is disclosed, for example, in the applicant's prior patent application publication Fl 20055121. In said machine, the length of the log to be cut off the trunk can be adjusted by changing the position of the cross-cutting device, and the length of the splitting stroke is adjusted according to the length of the log by moving the splitting head first to a suitable initial position depending on the length of the log to be split, before the actual splitting stroke is started. Normally, this adjusting movement is performed before the cross-cutting is started. After the adjusting movement, the interspace between the splitting head and the cross-cutting blade is by only a small clearance longer than the log to be cut, so that the log has sufficient space to move from the cross- cutting device to the interspace between the splitting head and the splitting blade, but there is no empty space between the splitting head and the log to require an unnecessary movement of the splitting cylinder, even if the length of the cross-cut log were significantly shorter than the maximum length of the stroke of the splitting cylinder. Thanks to this, the time taken by the actual splitting stroke becomes shorter when the logs are shorter than the maximum length of the stroke of the splitting cylinder.

However, a drawback in wood chopping machines of prior art, in which the length of the stroke can be adjusted according to the length of the log cut off the trunk, has been, among other things, the necessity to use complex mechanical auxiliary devices for adjusting the length of motion of the splitting cylinder, such as various lever mechanisms which are movable/turnable by spring force and which control the control valve of the splitting cylinder and/or several separate control valves separate from the control valves of the other actuators of the wood chopping machine, for implementing the adjustment irrespective of the other functions of the wood chopping machine. In particular, such mechanical solutions become complicated if the wood chopping machine features the adjustment of the length of the log to be split. On the other hand, both the adjustment of the length of the stroke and the adjustment of the cross-cutting point could be implemented, for example, by electrical or electronic systems. However, these electrical and/or electronic control systems which would simplify the mechanics have been intentionally avoided, because electrical devices and/or electronics which would be sensitive to use and storage primarily outdoors have been unwanted in the equipment.

It is an aim of the present invention to disclose a method for making firewood and a corresponding wood chopping machine to eliminate the above- mentioned drawbacks involved in the prior art. In particular, it is the aim of the invention to disclose a method and a wood chopping machine, in which the adjustment of the length of motion of the splitting head is implemented in a simpler and more reliable way than before but still in such a way that it can also be implemented totally without the use of electricity and electronics. Furthermore, it is an aim of the invention to disclose a wood chopping machine, in which the movement of the splitting cylinder and the other actuator-driven functions of the wood chopping machine can be controlled, at least partly, by the same control valve, wherein the number of valves needed for controlling the actuators driving the different functions becomes smaller than before. Furthermore, it is an aim of the invention to disclose a wood chopping machine, in which the adjustment of the length of the log to be crosscut does not require a complex and expensive mechanical control system and not necessarily even an electrical and/or electronic control system.

The method according to the invention is characterized in what will be presented in the characterizing part of claim 1 , and the wood chopping machine according to the invention is characterized in what will be presented in the characterizing part of claim 2.

The inventive idea of the method and the wood chopping machine according to the invention is that the length of motion of the splitting cylinder of the wood chopping machine is adjusted by by-pass valves which are connected to the pressurized medium channels of the splitting cylinder and which stop the movement of the movable head of the splitting cylinder by guiding the pressurized medium that moves the piston of the splitting cylinder past the splitting cylinder (for example, to a return duct for pressurized medium). The by-pass valve, in turn, is controlled by a control means which is coupled to the moving end of the splitting cylinder and which switches the by-pass valve on after the control means has moved with the movable end to the desired stopping position. The by-pass valve can be switched on mechanically or electrically; in other words, it is possible to use either mechanical control or alternatively at least partly electrical control.

The method and the wood chopping machine according to the invention give significant advantages to the methods of making firewood and the wood chopping machines of prior art. In the method and the wood chopping machine according to the invention, no complex mechanisms or electronics which are susceptible to disturbances in outdoor conditions will be required for adjusting the length of the stroke of the splitting cylinder, but the length of motion of the splitting cylinder is adjusted with by-pass valves which can be switched on depending on the position of the movable end of the splitting cylinder, for example with a very simple mechanical control means. Thanks to its control with the by-pass valves, the splitting cylinder can be switched to the same pressurized medium circuit with the actuators which operate the feeding device and/or the cross-cutting device and are driven by pressurized medium, wherein only one main control valve (for example, a 3-way valve) is needed for controlling the whole machine. For these reasons, the wood chopping machine can be made much simpler, more reliable and less expensive in its manufacturing costs than before, but still equipped with functional properties which correspond to the wood chopping machines of prior art in which the length of the stroke of the splitting cylinder is adjusted according to the length of the log. Furthermore, thanks to such a method, the adjustment of the length of the log to be cut off a trunk can be implemented in a very simple way, either depending on or independently of the length of the log to be cut off.

In the following, the invention will be described in more detail with reference to the appended drawings, in which Fig. 1 shows a principle chart of a wood chopping machine according to the invention,

Fig. 2 shows the initial position of the splitting cylinder and the cross- cutting device of the wood chopping machine of Fig. 1 , seen from the side, during splitting of a full-length log,

Fig. 3 shows the initial position of the splitting cylinder of the wood chopping machine of Fig. 1 , seen from the side, during splitting of a log that is clearly shorter than a full-length log,

Fig. 4a is a principle drawing illustrating an alternative way of adjusting the length of the stroke of the splitting cylinder of the wood chopping machine,

Fig. 4b is a principle drawing illustrating another alternative way of adjusting the length of the stroke of the splitting cylinder of the wood chopping machine, and

Fig. 4c is a principle drawing illustrating a third alternative way of adjusting the length of the stroke of the splitting cylinder of the wood chopping machine.

Figures 1 to 3 shows a wood chopping machine operating according to the method of the invention. Here, the sawing motion of the cross-cutting device is generated by means of a manually operated turning handle 8. Figure 1 only shows the parts of the wood chopping machine which are most essential in view of the invention. Figures 2 and 3 are also limited to illustrate these most essential elements of the invention. For example, various details of the frame 1 of the machine, as well as protecting structures belonging to the frame, such as a protection cage to be turned on top of the splitting device, can be mainly implemented, for example, in any suitable way known as such.

In addition to the frame 1 , the wood chopping machine shown in Figs. 1 to 3 also comprises a feeding device 2, a cross-cutting device 3 and a splitting device 4. As shown in Figs. 2 and 3, the feeding device 2 is a belt conveyor. Here, a tree trunk 5 is stopped by a stopping member 7 placed after the belt conveyor 6 of the feeding device 2 and fixedly mounted on the frame 1 of the wood chopping machine, in the direction of travel of the tree trunk 5, at a small distance L _v from the splitting blade 13 of the splitting device 4 farther behind the conveyor belt 6. In the wood chopping machine shown in Figs. 1 to 3, the cross-cutting device 3 is a chain saw 9 which can be turned against the tree trunk by a manual turning handle 8 and which is shown in Figs. 2 and 3. The splitting device 4 comprises a splitting cylinder 10, a splitting head 1 1 , a splitting chute 12, and a splitting blade 13. The splitting cylinder 10, the splitting chute 12 and the splitting blade 13 are mounted on the frame

I of the wood chopping machine in a way known as such. In this case, the splitting cylinder 10 is a double-acting hydraulic cylinder. The splitting head

I 1 is a rectangular or cylindrical piece made of, for example, a metal sheet and fixed to the movable end of the splitting cylinder 10. The feeding device 2 and the cross-cutting device 3 are also devices driven by hydraulic actuators. Consequently, all the actuators of the wood chopping machine can be connected to the same hydraulic system, and they can all be controlled by hydraulic control valves.

As shown in Fig. 1 , the wood chopping machine comprises only one main control valve 14 for controlling the feeding device 2, the cross-cutting device 3 and the splitting device 4, all connected to the same hydraulic fluid circuit 20. Furthermore, the hydraulic fluid circuit 20 controlled by the main control valve 14 comprises one protection valve 15 and two by-pass valves 16a and 16b, as well as four non-return valves, of which the valves 17a and 17b are in connection with the hydraulic motor 18 of the feeding device 2 and the other two in connection with the chain saw (not shown in Fig. 1 ). The protection valve 15 is used to prevent the starting of the device if the protection cage (not shown in the figure) on top of the feeding device 2, the cross-cutting device 3 and the splitting device 4 is in the open position. The by-pass valve 16a is a by-pass valve that causes stopping of the work movement of the splitting cylinder 10, and the by-pass valve 16b is a by-pass valve that causes the stopping of the return movement (hereinbelow, the bypass valve 16a for the work movement and the by-pass valve 16b for the return movement). The non-return valves 17a and 17b for the feeding device are coupled, as shown in Fig. 1 , in such a way that they prevent the backwards rotation of the hydraulic motor 18 of the feeding device that runs the conveyor belt 6. The purpose of this is to keep the conveyor belt 6 stationary when the splitting cylinder 10 performs a return movement. The non-return valves in connection with the chain saw 9 are, in other respects, arranged in a corresponding way, but they are coupled the other way around, that is, in such a way that the hydraulic motor of the chain saw (not shown in the figures) runs when the splitting cylinder 10 performs a return movement, but remains stationary when the splitting cylinder 10 performs a work movement.

In this embodiment, the main control valve 14 is controlled with the turning handle 8 for turning the chain saw 9 upwards and downwards. At the same time, the turning handle 8 moves the stem 14a of the main control valve 14 between the positions A to C shown in Fig. 1. In Fig. 1 , the positions of the main control valve are indicated by letters A = feeding position (turning handle 8 up), B = stopping position (turning handle 8 in the middle) and C = sawing position (turning handle 8 down). It should further be noted that when the turning handle 8 is in the position C, the chain saw 9 is connected to the hydraulic fluid circuit 20 controlled by the main control valve 14, even though this is not illustrated in Fig. 1.

The by-pass valves 16a and 16b effective on the function of the splitting cylinder are 2-way valves with spring return, controlled by pressing the stem 19a or 19b in them. If the stem is not pressed, the by-pass valve remains closed, due to its spring return; that is, it prevents hydraulic fluid from flowing through the by-pass valve past the splitting cylinder to the return duct of the hydraulic fluid circuit 20. If the stem is pressed, the by-pass valve opens, wherein hydraulic fluid is allowed to flow past the splitting cylinder 10 directly to the return duct (in which case the movement of the splitting cylinder is thus stopped). In this embodiment, the by-pass valves 16a and 16b are controlled fully mechanically by means of a control arm 21 connected to the splitting head 1 1 fixed to the movable end of the splitting cylinder 10. The end 21 a of the control arm 21 presses the stem of the by-pass valve after the splitting cylinder 10 has moved the splitting head 1 1 so that the end 21 a of the control arm 21 comes against the stem of the by-pass valve. The by-pass valve 16a for the work movement is connected to the hydraulic fluid channel 20a led to the chamber 10a of the splitting cylinder 10 on the side of the work movement, and the by-pass valve 16b for the return movement is connected to the hydraulic fluid channel 20b led to the chamber 10b of the splitting cylinder on the side of the return movement. Consequently, the by-pass valve 16a for the work movement stops the work movement, and the by-pass valve 16b for the return movement stops the return movement.

In the embodiment shown in Figs. 1 to 3, the by-pass valve 16b for the return movement is connected to an adjustment table 22 that can be moved in the direction of movement of the splitting head (in the longitudinal direction of the wood trunk to be crosscut) and locked in the desired position in the frame 1 of the wood chopping machine. Thus, the distance between the by-pass valve 16b for the return movement and the splitting blade 13 of the splitting device 4 can be adjusted by changing the position of the adjustment table 22. Thanks to this, the adjustment table 22 can be used for adjusting the length of the stroke of the splitting cylinder 10, because when the adjustment table 22 is moved closer to the splitting blade 13, the by-pass valve 16a for the return movement, connected to the adjustment table 22, will stop the return movement of the splitting cylinder 10 before the preceding position of the adjustment table 22; in other words, the return movement and thereby also the next work movement will become shorter than before the adjustment. In a corresponding manner, when the adjustment table 22 is moved farther away from the splitting blade 13, the return movement and thereby also the next work movement will become longer than in the situation before the adjustment.

In the embodiment shown in Figs. 1 to 3, the chain saw 9 used as the cross- cutting device 2 of the wood chopping machine is also connected to the adjustment table 22. The point of connection of the chain saw 9 is selected so that its guide bar 9a is by a small distance L _p in front of the splitting blade 13 in the direction of movement of the splitting head 1 1 of the splitting device 4 when it is in its stopping position after the return movement. Because the length of the control arm 21 is constant, the movable end of the splitting cylinder 10 and the splitting head 1 1 connected to it will, after the return movement, always stop at the same distance from the by-pass valve 16b for the return movement connected to the adjustment table 22; that is, the stopping position after the return movement of the splitting head is always the same in relation to the adjustment table 22, irrespective of the position in which the adjustment table 22 has been adjusted. Furthermore, because the stopping member 7 for stopping the feeding of the tree trunk 5 has stopped the trunk 5 before the cross-cutting so that its end is, in the above-described manner, by a small distance L _v in front of the splitting blade, the log 23a or 23b crosscut from the trunk by the chain saw 9 will always be of a suitable size fitting between the splitting head and the splitting blade (in other words, shorter by the small distances L _v and L _p than this gap). Consequently, in the embodiment of the wood chopping machine shown in Figs. 1 to 3, it is possible to use the adjustment table 22, adjustable in the direction of movement of the splitting cylinder 10, to adjust both the length of the log 23a or 23b to be split from the tree trunk 5, and the length of the splitting stroke of the splitting cylinder 10. Figure 2 shows the position of the adjustment table 22 and the log 23a in the splitting chute 12 when the length L _1a of the log has been adjusted as long as possible (in which case the length L _2a of the stroke of the splitting cylinder is equal to its maximum stroke length SL _max ), and Fig. 3 shows the position of the adjustment table 22 and the log 23b in the splitting chute 12 when the length L _{1 b} of the log has been adjusted clearly shorter than the maximum length, in which case the length L _2b of the stroke of the splitting cylinder is clearly shorter than maximum stroke length

^Lm _3x .

In the embodiment of Figs. 1 to 3, the movability of the adjustment table 22 is implemented so that the adjustment table 22 is mounted on bearings at its first edge (the edge on the side of the machine frame), by means of sleeves

24 fixed to this edge, to a bar 25 extending in the direction of movement of the splitting cylinder and mounted in the frame 1 so that the table can be turned (with respect to the bar) with a handle 26 from the horizontal position upwards and back to the horizontal position, as well as moved along the bar

25 in the direction of movement of the movable end of the splitting cylinder 10 back and forth closer to or farther away from the splitting blade 13. The locking of the adjustment table 22 in its position, in turn, is implemented in such a way that the edge of the adjustment table opposite to the edge fixed to the bar (the outer edge of the adjustment table) is provided with a toothing 27 extending downwards from the lower surface of the table for locking the adjustment table to a horizontal locking pin 28 below the adjustment table when the adjustment table is turned against this locking pin 28 so that it is placed between the teeth of the toothing 27. In other words, when the adjustment table is adjusted, its outer edge is first lifted slightly (wherein the table is tilted), so that the locking of the table is released. After this, the table is moved in the desired manner either closer to or farther away from the splitting blade. At the desired location, the adjustment table is lowered back to the horizontal position so that the locking pin 28 fixed to the frame is placed in the nearest interspace between two teeth of the toothing 27. Thus, the table is locked in its position. In this embodiment, the adjustment is thus stepped. Furthermore, there may be a measuring scale (not shown in the drawings) or another suitable measuring tool between the edge of the table and the frame, to indicate the length of the log 23a or 23b to be cut off.

For applying the wood chopping machine of Figs. 1 to 3, the adjustment table 22 is adjusted, in the above-described manner, to the desired distance from the splitting blade 13 of the splitting device 4 and the stopping member 7 of the feeding device 2, according to the length of the firewood to be made. After this, the first tree trunk to be used as raw material for firewood is lifted onto the conveyor belt 6 of the feeding device 2. When the first trunk is on the conveyor belt 6, the machine is started by turning the handle 8 upwards from the stopping position to the feeding position. Thus, the stem 14a of the main control valve 14 connected to the turning handle moves from the position B to the position A, wherein the feeding device 2 is started and the splitting cylinder 10 of the splitting device 4 starts a work movement (the first work movement and return movement of the splitting cylinder take place without a log to be split, if this is the first tree trunk to be fed into the machine). The conveyor belt 6 moves the tree trunk 5 against the stopping member 7, and the splitting cylinder 10 of the splitting device 4 moves the splitting head 1 1 so that the control arm 21 pushes the stem 19a of the bypass valve 16a for the work movement to the bottom, wherein the by-pass valve 16a for the work movement is opened and the work movement is stopped in the stopping position of the work movement. After this, the cross- cutting of the tree trunk 5 is started by turning the turning handle 8 downwards to the cross-cutting position. Thus, the stem 14a of the main control valve 14 moves to the position C, wherein the chain saw 9 is started and the splitting cylinder 10 starts the return movement. When the turning handle 8 is pressed further downwards, the chain saw 9 turns against the trunk 5 and crosscuts it so that the trunk 5 becomes a first log (23a or 23b). In the meantime, the splitting cylinder 10 has moved the splitting head 1 1 to the stopping position of the return movement, where the end 21 a of the control arm 21 has pressed the stem 19b of the by-pass valve 16b for the return movement to the bottom, wherein the by-pass valve 16b for the return movement has opened and the return movement of the splitting cylinder 10 has stopped. After the trunk 5 has been crosscut, the log formed drops to the splitting chute 12 after the conveyor belt 6, between the splitting head 1 1 and the splitting blade 13 (as shown in Figs. 2 and 3). After this, the turning handle 8 is turned up to the feeding position again. Thus, the stem 14a of the main control valve 14 moves to the position A, wherein the feeding device 2 is started and the splitting cylinder 10 starts the work movement. The feeding device 2 moves the remaining trunk 5 against the stopping member 7 again. At the same time, the splitting cylinder 10 performs a splitting stroke, wherein the log, dropped into the splitting chute 12 after the cross-cutting, is pushed through the splitting blade 13 and is split into billets. After this, the turning handle 8 is turned down again, wherein the chain saw 9 crosscuts a new log from the trunk 5 that was moved against the stopping member again, and the splitting cylinder 10 performs a return movement; that is, the splitting head 11 moves from the stopping position of the work movement to the stopping position of the return movement, wherein a new log fits to drop between the splitting head 1 1 and the splitting blade 13 again. From this step on, the use of the device is continued in the above-described manner. When the last log, that is, the remnant piece of the same trunk has come to cross-cutting, the trunk no longer needs to be crosscut but the remnant piece is transferred by the feeding device 2 directly to the splitting chute 12 by turning the turning handle 8 to the feeding position, wherein the conveyor belt 6 moves the remnant piece forward so that it drops into the splitting chute 12. From this step on, the making of firewood can be continued by lifting tree trunks onto the conveyor belt 6 as the preceding trunks have been split into billets. Finally, the wood chopping machine is stopped by turning the turning handle 8 to the stopping position, wherein the stem of the main control valve moves to the position B, in which the flow of hydraulic fluid to the feeding device 2, the cross-cutting device 3 and the splitting device 4 is prevented.

In many respects, the wood chopping machine according to the invention can be implemented in a way different from the above-described example embodiment. For example, the feeding device may be, instead of a belt conveyor, for example a slat conveyor, a roller conveyor, or any other suitable conveyor for moving a tree trunk against a stopping member after the feeding conveyor. In the simplest devices, the feeding conveyor can also be replaced with a feeding chute or, for example, a roller table equipped with freely rotating rollers, on which the trunk is moved forward by manual force. The cross-cutting device may be, instead of a chain saw that is turned manually against the tree trunk, a chain saw that performs the cross-cutting movement by means of an actuator, or, alternatively, for example a circular saw.

Alternatively, the adjustment of the stroke of the splitting cylinder may also be implemented so that the length of the stroke is adjusted by moving the bypass valve for the work movement, or so that the adjustment is made by moving both of the by-pass valves with respect to the splitting cylinder. It should further be noted that such an adjustment of the length of the stroke is also possible in such a wood chopping machine, in which the length of the log to be crosscut from the trunk is not adjustable, that is, in which the distance between the cross-cutting device and the splitting head is constant. Thus, the aim of the adjustment is primarily to optimize the splitting movement to a length that is as suitable as possible, to provide an operation that is as efficient and productive as possible.

The wood chopping machine may also be more automatic than the above- presented embodiment. Thus, for example the stopping member may be equipped with a mechanical control valve or an electrical switch to start the sawing movement and to stop the feeding of the trunk automatically for the time of sawing of the trunk. Furthermore, among other things, the adjustment table that determines the length of the log may be steplessly adjustable, wherein it may be implemented, for example, in such a way that it is mounted on guides, along which it can be moved (adjusted) and to which it can be locked, for example by means of a clamping screw or a hydraulic locking brake, in any desired position. Naturally, the adjustment table may also be adjustable by an actuator. In some embodiments, the by-pass valves that stop the working and return movements of the splitting cylinder may not be controlled by a mechanical control arm but by means of electrical switches or contactless sensors {e.g. inductive or optical sensors). In the case of electrical control, the by-pass valves used may be magnetic valves which are opened and closed by electrical control. In this case, however, the wood chopping machine will require a separate electrical system or a connection to an electrical power network.

In the wood chopping machine according to the method of the invention, it is possible to use many various ways of adjusting the length of the log to be cut off the trunk and/or the length of the splitting stroke. Figures 4a to 4c show alternative ways for implementing the adjustment of the splitting stroke with respect to the embodiment shown in Figs. 1 to 3. Figures 4a to 4c show the position of a cross-cutting device 31 and a splitting head 32 during the splitting of a log 30 that is clearly shorter than the maximum stroke length SL _max of the splitting cylinder 33. To the length L ₁ of this log 31 corresponds the length L ₂ of the splitting stroke, which is longer than the length L ₁ of the log by approximately the distance L _p between the splitting head and the guide bar 35 of the cross-cutting device 31.

In the embodiments shown in Figs. 4a and 4b, the cross-cutting device 31 is moved by means of a separate transfer cylinder 34. Thus, the cross-cutting device 31 can be moved before the splitting stroke or during the preceding splitting stroke to the position shown in Fig. 4a, wherein its guide bar 35 is by the distance L _p in front of the splitting head 32 when the splitting head 32 is in the stopping position after the return movement. In fact, the way of adjusting the length of the stroke in Fig. 4a corresponds to the situation of Figs. 1 to 3 in that also in the case of Figs. 1 to 3, the cross-cutting device 31 is, in the initial phase of the splitting stroke, at the distance L _p in front of the splitting head 32, but after the splitting stroke has started, it remains in this place; that is, the distance L _p changes during the splitting stroke. In the situation of Fig 4a, the difference to the embodiment of Figs. 1 to 3 is, however, that the adjustment of the cross-cutting device 31 is effected not by an adjustment table but by a separate transfer cylinder 34, and the adjustment of the splitting stroke can be performed separately from a possible adjustment table. Another alternative is to operate as shown in Fig. 4b, that is, in such a way that the distance L _p between the splitting head 32 and the guide bar 35 of the cross-cutting device 31 remains constant all the time, wherein the cross-cutting device follows the movements of the splitting head 32. Thus, the splitting cylinder 33 performs a reciprocating motion but stops during the work movement at the adjusted distance from the splitting blade 36 for the time of cross-cutting of the trunk. In the methods of adjusting the length of the splitting stroke according to Figs. 4a and 4b, the transfer cylinder 34 can be controlled manually or automatically {e.g. with by-pass valves) in such a way that the control arm moved by the movable end of the transfer cylinder 34 stops the cross-cutting device at the desired adjusted distance L _p from the splitting head, when the splitting head is in the initial position (in the embodiment of Fig. 4a), or in such a way that the cross-cutting device follows the work and return movements of the splitting head (according to Fig. 4b), wherein the cross- cutting device remains all the time at the distance L _p from the splitting head. Alternatively, the arrangement of Fig. 4b can also be implemented in the way shown in Fig. 4c so that the cross-cutting device 31 is connected to the splitting head by suitable fastening members 37. Thus, it will be sufficient to control the length of the splitting stroke of the splitting head 32, because it simultaneously determines the length of the log 30 to be cut off the trunk.

It should also be noted that the by-pass valves playing a central role in the method of the invention can also be used for stopping and controlling the movements and/or operation of other devices of the wood chopping machine than the splitting cylinder. For example, the conveyor belt of the feeding conveyor can be stopped with a by-pass valve that stops the hydraulic motor of the feeding conveyor when the tree trunk hits the stopping member, or the movement of the saw chain of the cross-cutting device can be stopped with a by-pass valve that is switched on and stops the motor of the chain saw after the guide bar has moved below the line of travel of the trunk. Moreover, it is not always necessary to switch the by-pass valves directly to the return duct of pressurized medium. In some embodiments, the by-pass valve for controlling the function of the first actuator may be arranged to operate in such a way that when it guides the pressurized medium past a first actuator, it guides it to a second actuator whose operation is thus started after the operation of the first actuator has been stopped. By this kind of control, the same pressurized medium can be used for controlling several actuators coupled one after the other by means of by-pass valves.

The invention is not limited to the above-presented advantageous embodiments, but it may vary within the scope of the inventive idea presented in the appended claims.