WO2000015026A1

WO2000015026A1 - A control arrangement and a method in a delimbing device

Info

Publication number: WO2000015026A1
Application number: PCT/FI1999/000734
Authority: WO
Inventors: Petri Niemi
Original assignee: Timberjack Oy
Priority date: 1998-09-15
Filing date: 1999-09-10
Publication date: 2000-03-23
Also published as: FI104353B; SE0100786D0; FI981983A0; SE520146C2; SE0100786L; AU5626399A

Abstract

The invention relates to method in a delimbing device, which delimbing device (1) comprises a frame structure (2), at least one supporting means (3a, 3b, 3c) attached in the frame structure (2) in a movable (5a, 5b, 5c) manner to support the tree-trunk (S) and to exert a first force effect (F0) on the tree-trunk (s), actuator means (9) for controlling the position of the supporting means (3a, 3b, 3c) to maintain the first force effect (F0) exerted by the supporting means (3a, 3b, 3c) on the tree-trunk (S), first sensor means (11) for measuring the diameter (D) of the tree-trunk(s) and a control system (10) for controlling at least the actuator means (9). In the method the distance (E) of the tree-trunk (S) with respect to a set reference level (2d) is monitored preferably in a continuous manner by means of second sensor means (12) arranged in connection with the device (1) and coupled to the control system (10), and that the distance (E) is compared in the control system (10) with a set maximum value (E2, E3) of the distance (E) and/or a set manimum value (E1, E4) are stored to compare the distance with these values (E1, E2, E3, E4) to control at least the actuator means (9) by utilizing the information obtained from the comparison.

Description

A control arrangement and a method in a delimbing device

The invention relates to a method in a delimbing device according to the preamble of claim 1. The invention also relates to a method according to the preamble of claim 8 for measuring a tree-trunk in a delimbing device. The invention also relates to a delimbing device according to the preamble of claim 9.

As is well known, a harvesting head, i.e. a multifunctional grapple, coupled to a harvester, i.e. a multifunctional machine, is used for processing of tree-trunks, the function of which grapple is to grip the vertically growing tree, to crosscut the tree and to bring it into a substantially horizontal position to be further processed. For this purpose, the multifunctional grapple is coupled in an articulated manner to a boom construction in the multifunctional machine, and the necessary actuators, typically hydraulic cylinders and hydraulic motors are connected therein, and by means of them it is possible to utilize the position of the multifunctional grapple and its different functions. The multifunctional grapple, which in the description hereinbelow will also be referred to as a delimbing device, typically comprises means provided in pairs for supporting the tree-trunk, wherein these means are typically equipped with delimbing members for delimbing the branches at the same time when the tree-trunk is driven through the multifunctional grapple in the longitudinal direction of the tree-trunk. For this purpose, the multifuctional grapple is typically provided with feed rolls or feed tracks functioning by means of hydraulic motors and pressing themselves against the trunk, pulling the trunk past delimbing blades by means of friction. The multifunctional grapple can also be provided e.g. with spring-loaded auxiliary delimbing blades, to improve the delimbing quality throughout the tree-trunk. The multifunctional grapple may also be provided with another pair of supporting means for supporting the tree-trunk, and it is also possible to connect delimbing member thereto. The multifunctional grapple is also provided with a chainsaw by means of which the tree-trunk is crosscut into a desired length by stopping the feeding of the trunk and by activating the sawing. After the crosscutting, the feeding of the tree-trunk proceeds, until the entire tree-trunk has been processed. One above-described device is presented in the patent publication EP 0 473 686-B1 , which device is provided with four delimbing members arranged in pairs to move in an articulated manner, and also with one auxiliary delimbing member fixed in the frame structure in an immovable manner. This stationary delimbing member also comprises a supporting surface against which the tree-trunk is pressed by means of the first pair of delimbing members. The delimbing blades are closed and opened by means of a hydraulic cylinder coupled therebetween in an articulated manner. There are also known devices, in which the tree- trunk is pressed against the frame structure of the device by means of delimbing blades, the frame structure being provided with a supporting surface against which the tree-trunk slides at the same time during the delimbing process. Thus, the auxiliary delimbing member, which is connected to the frame in an articulated manner, can be arranged to move with respect to the frame structure and to be pressed against the tree-trunk e.g. by means of spring force. A delimbing device equipped with a mobile, spring-loaded auxiliary delimbing member is disclosed for example in the patent publication EP 0 346 308-B1 , and in the corresponding US patent 4,898,218. In the latter solution, the supporting means and the delimbing members attached thereto are, however, locked in an immovable manner into a particular position by means of cylinders, and the position is changed only when it is discovered that the diameter of the tree-trunk has decreased a predetermined amount. Thus, the supporting means are closed a desired amount, so that the tree is positioned on a higher level in the delimbing device. In the device in question, the reference level is formed by the point in which the limit switch becomes effective.

Another drawback of the device presented in the publication US 4,898,218 is that the device does not take into account the growth of the diameter of the tree-trunk or the fact that the tree-trunk becomes lighter during the delimbing, wherein the result is an excessive force effect exerted by the delimbing blades on the tree-trunk. Therefore the invention is poorly applicable to devices with an integrated auxiliary delimbing member or in which the tree-trunk is supported against a supporting surface. Yet another drawback of the presented device is that the user cannot change the position of the distance indicated by the limit switch during the delimbing, but this has to be conducted mechanically by changing the fixing point of the limit switch. Yet another drawback is that by means of the device the position of the tree-trunk is not known for example when the distance of the tree-trunk is closer to the position indicated by the limit switch. Thus, errors occur in the diameter measurement.

In the multifunctional grapples coupled to multifunctional machines, the tree-trunk which is placed in a substantially horizontal position is typically processed in such a way that the articulation of the frame structure of the multifunctional grapple and the delimbing blades is located above the tree-trunk, wherein the opening of the delimbing members and the supporting means makes the tree-trunk fall downwards. There are also known devices for processing elongated tree-trunks, which correspond to the multifunctional grapple and in which the crosscut trunks are lowered with a working machine, such as a crane, and the above-described operations are conducted. However, in these devices the frame structure and the articulations are placed below the tree-trunk, and the delimbing members are opened upwards, wherein the weight of the tree-trunk does not have the tendency to open the delimbing blades, and the tree-trunk rests on the frame of the device.

In the apparatus coupled to the multifunctional device the aforementioned supporting surface is located against the upper surface of the tree-trunk when the tree-trunk is in a horizontal position. The supporting means press the tree-trunk against the supporting surface by means of hydraulic cylinders, wherein at the same time said supporting surface forms a fixed reference surface for determining the diameter of the tree-trunk. As is well known, the position of the delimbing blades and the supporting means is used for measuring the diameter, for example by utilizing a sensor recognizing the position of the hydraulic cylinder used for closing and opening the delimbing blades and the supporting means. There are known linear sensors which indicate the range of the piston rod of the hydraulic cylinder. The articulation of the delimbing blades can also be equipped with sensors, e.g. a potentiometer, which sensor indicates the rotation of the joint when compared to their reference position. By placing the sensors inside the joints, a durable structure is attained which is protected even against demanding environmental conditions. By means of the control system of the multifunctional machine, it is possible to determine the diameter of the tree-trunk calculatorily on the basis of the position of the supporting means, at the same time presuming that the tree-trunk is positioned against the reference surface, i.e. the supporting surface. This information is used together with the results of the length measurement to calculate and report the processed quantities of timber, the generated costs, the volume of the quantity of timber as well as the basis for the provisions. Thus, it is obvious that this causes extremely high demands for the accuracy of the measurement, so that the information on the processed quantities of timber would be as accurate as possible.

One factor which causes errors in the diameter measurement is that when the tree is processed in horizontal position, the weight of the tree- trunk causes the opening of the downward directed supporting means, wherein at the same time the tree-trunk is detached from the reference surface. When the diameter is determined on the basis of the position of the supporting means, the diameter is thus interpreted to be too large. Thus, the user of the multifunctional machine typically increases the pressure level of the actuators of the supporting means to a high level so that the force effect of the supporting means would be sufficient in different situations to support the tree-trunk and to press it against the reference surface as disclosed in the patent publication EP 0 473 686-B1.

However, because of the raised pressure level, the supporting means and the delimbing members tend to be pressed against the tree-trunk with an unnecessarily strong force during the delimbing, especially as the tree-trunk becomes thinner from down below to the top and in the direction of delimbing. When the tree-trunk becomes thinner, the loading caused by the same on the delimbing device is decreased when the weight is reduced and the tree is transferred during the delimbing. When the delimbing blades are strongly pressed against the tree-trunk, the necessary friction forces for feeding the tree-trunk through the device are also increased. Thus, the forces required by the feed rolls are increased and at the same time the feed rolls have to be pressed harder against the tree-trunk to attain sufficient friction, or more efficient friction means have to be arranged in the feed rolls. Along with the higher forces, the friction forces of the components are also increased and a larger portion of the efficiency of the devices is utilized to overcome these friction forces. The consequences also include an increase in the damages of the tree-trunk, a weakening of the quality and large, efficient components.

In different seasons, the softness of the surface structures of the tree- trunk varies, which increases the liability for damages. During the delimbing of the tree-trunk the user has to otherwise control the delimbing device and the working machine, and thus the pressure levels and their fluctuation limits are typically set for the entire tree-trunk at the same time, generally they are set constant for each diameter area. Typically, the pressure level is set unnecessarily high, so that there would be no errors in the diameter measurement, and the tree- trunk would always be supported with a sufficient force even at varying conditions. The consequences are, however, the above-described problems.

The selection of the pressure levels conducted by the user for different situations is difficult, and the best result is based on the long-term experiences of the user him/herself. When the seasons and weather conditions change, the density of the wood material, the softness of the surface section of the wood, the structure of the surface section, the amount of resin and the humidity also change, and thus it takes a considerably long time before the user adjusts to the different conditions and before a good delimbing result is attained by means of the delimbing device. Other effective factors include the variations in the shape of the tree-trunk, the number of branches to be delimbed and the variations in their size, as well as for example the dirtiness of the tree-trunk. It is difficult even for an experienced user to be prepared for the changes in the conditions, and it may take a considerable amount of time to determine the conditions and to find the pressure levels in each working location, which can result in wood material of bad quality as well as in a bad delimbing result at the initial working stages.

The purpose of the present invention is to eliminate the above- described drawbacks, thereby improving the state of art prevailing in the field. To attain these purposes, the method according to the invention in a delimbing device is primarily characterized in what will be presented in the characterizing part of the appended claim 1. The method according to the invention for measuring the tree-trunk in a delimbing device is primarily characterized in what will be presented in the characterizing part of the appended claim 8. The delimbing device according to the invention is primarily characterized in what will be presented in the characterizing part of the appended claim 9.

With the invention, several considerable advantages are achieved, by means of which for example the processing of tree-trunks is accelerated and it also becomes more effective, and the damages in the tree-trunks are avoided. A central principle of the invention is to determine the position of the tree-trunk in the device, on the basis of which correcting measures are conducted either by the user or by the control system of the device. By determining the position it is also possible to check, correct or complement the information obtained from the diameter measurement. With the invention it is also possible to control the position of the tree-trunk as well as the forces exerted thereon considerably better than in prior art.

The user adapts to different conditions and learns to use the device considerably faster when compared to prior art, when it is indicated for the user, according to a preferred embodiment of the invention, when the position of the tree-trunk has changed, especially when it has moved further than the maximum value from the reference surface of the delimbing device. On the basis of the indication the user can conduct the necessary correction measures, for example the user can set the pressure of the delimbing blades and the supporting means into a suitable value. The pressing force of the supporting means can be set to a level, which, on one hand is sufficiently high for holding the tree- trunk, and on the other hand sufficiently low to avoid too high pressing forces and friction forces exerted on the tree-trunk.

A further advantage is that with the information given by means of the indication or otherwise in connection with the same, the users obtain further information on the system, wherein the device can be used more effectively, and it is possible to accelerate the process of learning to use the device and making correct estimations in different conditions. When necessary, the tree-trunk can be driven through the delimbing device again to correct the diameter measurement, if the distance of the tree-trunk has been too large, and thus the information obtained from the measurement of the tree-trunk is more reliable. In addition, the work is accelerated, because the test drives for testing the pressure levels set by the user as well as the re-checkings for measurement corrections can be abandoned or the number of these processes can be considerably reduced.

Another considerable advantage of the invention is that the position of the tree-trunk with respect to the delimbing device remains substantially constant. For example the shape of the delimbing members is optimized in such a way that when the diameter of the tree-trunk varies, and when the tree-trunk is supported against the stationary supporting surface of the delimbing device, the position of the delimbing blades enables an efficient and even delimbing result all over the tree-trunk. The change of the position is monitored in a simple manner by examining whether the distance is smaller or greater than the set threshold value.

According to a preferred embodiment of the invention, the volume or pressure control of the actuators of the delimbing device can also be implemented automatically by the control system of the delimbing device. Thus, on the basis of the information received from the measurement of the distance, the control system adjusts the volume flow of the components affecting the supporting means. The adjustment is continued until the desired position of the tree-trunk is achieved. At the same time the pressure of the components is adjusted, wherein the force effect exerted by the supporting means on the tree-trunk as well as the force effect exerted by the tree-trunk on the delimbing device is simultaneously adjusted if the tree-trunk rests against the frame structure of the delimbing device. Thus, a considerable advantage is that it is not necessary for the user to take care of e.g. the selection of the pressure levels for different diameters of the tree-trunk, but the user can concentrate on the control of other functions of the delimbing device and the working machine to which the delimbing device is coupled. This also results in a system, which functions faster than prior art to correct error situations.

The advantage of the invention is also that the pressure level of the actuator means for different diameters of the tree-trunk can be adjusted in a stepless manner. Thus, a pressure adjustment which is considerably more accurate than the one pressure level determined for each diameter area. By adjusting and monitoring the pressure, the power consumption of the delimbing device can also be considerably reduced when compared to prior art.

Another advantage of the invention is that when necessary, the sensor means can be attached to the existing delimbing devices with very simple measures.

In the following description, the invention will be described by means of some preferred embodiments with reference to the appended drawings in which

Fig. 1 shows a perspective view of a delimbing device known as such in an upright position, the invention being applied in connection with the device,

Fig. 2a is a principle view illustrating the function of the supporting means and actuator means of the delimbing device of Fig. i , Fig. 2b shows a perspective view of the device and method according to a preferred embodiment of the invention, applied in connection with the delimbing device of Fig. 1 ,

Fig. 2c is a principle view illustrating the device and method according to another preferred embodiment the invention, applied in connection with the delimbing device of Fig. 1 ,

Fig. 3 illustrates schematically the act of determining the diameter of the tree-trunk conducted in connection with the delimbing device of Fig. 1 , as well as the correction of the diameter according to the invention, and

Fig. 4 illustrates schematically the placement of the pressure levels of the actuator means according to an embodiment of the delimbing device of Fig. 1.

With reference to Fig. 1 , a delimbing device 1 known as such comprises a frame structure 2. To couple the delimbing device 1 to the boom assembly (not shown in the drawing) of a working machine, e.g. a harvester, known as such, the device 1 also comprises a fixing structure 2a, which is attached to the frame structure 2 in a movable manner by means of an articulation 2b. With reference to Fig.1 , the device 1 is shown in a substantially upright (arrow Z) position, wherein by means of the articulation 2b and the fixing structure 2a, the frame structure 2 is arranged to rotate around a substantially horizontal (arrow X) direction. In the upper part of the fixing structure 2a, a fixing and rotating means 2c, such as a rotator 2c, is also arranged, to fix the device 1 in the end of the boom assembly of the working machine. By means of the fixing and rotating means 2c, the frame structure 2 is arranged to rotate around a substantially vertical (arrow Z) direction together with the fixing structure 2a.

The device 1 also comprises a first supporting means 3a and a second supporting means 3b, which are fixed in a movable manner to the frame structure 2 by means of articulations 5a and 5b. In the position according to Fig. 1 of the device 1 , the supporting means 3a and 3b are arranged to rotate around a substantially vertical (arrow Z) direction. The supporting means 3a and 3b are also equipped with delimbing members 4a and 4b to delimb the tree-trunk in a way known as such. The device 1 also comprises feeding means 6a and 6b, advantageously feed rolls 6a and 6b, which are placed against the tree- trunk to be delimbed and which utilize the driving effect exerted on the tree-trunk to pull the tree-trunk past the delimbing blades 4a and 4b to delimb the branches in the tree-trunk by means of the same. The feed rolls 6a and 6b are fixed in a movable manner to the frame structure 2 by means of articulations 7a and 7b, with which the feed rolls 6a and 6b are arranged to rotate around a substantially horizontal (arrow Y) direction with reference to Fig. 1.

The device 1 is in the position according to Fig. 1 when the tree-trunk extending substantially in the vertical (arrow Z) direction is gripped by means of the device 1 , wherein the supporting means 3a and 3b as well as the feed rolls 6a and 6b are advantageously in their outermost position according to Fig. 1 , to place the tree-trunk against the supporting surface 2d functioning as a reference surface of the frame structure 2. The supporting surface 2d is advantageously a plate-like metal plate 2d which in the position of the device according to Fig. 1 extends substantially in the vertical (arrow Z) direction and is integrated in the frame structure 2, the tree-trunk being held against the supporting surface 2d and sliding against the same during the delimbing process. The supporting surface 2d is advantageously located between the supporting means 3a and 3b. It is obvious that the reference surface can also be another surface or means, such as a wheel or a roll, against which the tree-trunk is pressed.

The device 1 also comprises cutting means 8 for cutting a standing tree-trunk which is to be delimbed. The cutting means 8, advantageously a chain saw 8, also conduct the cutting of the tree- trunk in parts of fixed length when it is supported by the supporting means 3a, 3b in a substantially vertical (arrow Y) direction. Thus, when compared to the position of Fig. 1 , the frame structure 2 has rotated substantially 90 degrees around the articulation 2d, wherein the supporting means 3a and 3b are directed substantially downwards in the vertical (arrow Z) direction, and for example the supporting surface 2d extends substantially in the horizontal (arrow Y) direction. To support the tree-trunk, the supporting means 3a and 3b are at least partly closed, wherein the supporting means 3a abuts on the tree-trunk on the opposite side of the tree-trunk with respect to the supporting means 3b. The supporting means 3a and 3b and their delimbing blades 4a and 4b have a curved shape so that they would conform with the shape of the tree-trunk as well as possible to delimb the branches on both side surfaces as well as on the bottom surface of the tree-trunk. In the above-described position the frame structure 2 with its supporting plates 2d is thus located primarily above the tree-trunk in the vertical (arrow Z) direction, and the supporting means 3a and 3b are primarily located on the sides of the tree-trunk and below the same. The device

1 also comprises an auxiliary delimbing member 4d, which, by means of an articulation 5d and in the position of the device 1 according to Fig. 1 , is arranged to rotate around a substantially vertical (arrow Z) direction. To delimb the upper surface of the tree-trunk, the auxiliary delimbing member 4d is pressed against the tree-trunk with its own weight or for example by means of a spring force or an actuator, such as a pressurized medium operated cylinder. When the tree-trunk is supported with the device 1 in a substantially horizontal (arrow Y) position, the auxiliary delimbing member 4d is primarily located above the tree-trunk.

The device 1 also comprises a measuring wheel 15 for measuring the length of the tree-trunk during the delimbing. The measuring wheel 15 is also utilized to determine how long a distance the tree-trunk has been fed in the delimbing device 1 , wherein the delimbing at the desired point can be performed by means of the cutting means 8. This measuring wheel 15 is arranged in connection with the frame structure

2 by means of an articulation known as such and for example a spring- loaded supporting arm, with which the measuring wheel 15 is arranged to follow the surface on the upper edge of the tree-trunk in a way known as such.

With reference to Fig. 1 , the device 1 also comprises a lower supporting means 3c with its lower delimbing blades 4c for supporting the tree-trunk at least from one side. The lower supporting means 3c is fixed to the frame structure 2 by means of an articulation 5c, wherein in the position according to Fig. 1 , the lower supporting means 3c is arranged to rotate around a substantially vertical (arrow Z) direction. The lower supporting means 3c is arranged for supporting the tree- trunk and keeping it stationary during the sawing, when the sawing is conducted by means of a sawing movement conducted by the cutting means 8 transversely through the tree-trunk. In the position of Fig. 1 , the cutting means, advantageously a chain saw, is arranged to rotate around a substantially vertical (arrow Z) direction. The supporting means 3a and 3b are located advantageously close to each other in the longitudinal direction of the tree-trunk, which in the position of the device 1 according to Fig. 1 corresponds to the substantially vertical (arrow Z) direction, and the lower supporting means 3c is arranged in a distance therefrom. In the device 1 according to Fig. 1 , the feed rolls 6a and 6b are arranged substantially on the opposite sides of the tree- trunk to exert an even traction on the tree-trunk. It is obvious that the lower supporting means 3c can be paired with a second lower supporting means, and there are also known apparatuses which lack the lower supporting means altogether.

In the delimbing process, the tree-trunk is moved substantially horizontally in its longitudinal direction, wherein the branches first strike against the delimbing blades 4a, 4b and 4d, and are cut off. Simultaneously by means of the supporting means 3a and 3b the tree- trunk is pressed against the frame structure 2, advantageously a supporting surface 2d. In the horizontal position of the tree-trunk the weight of the tree-trunk tends to open the supporting means 3a and 3b, wherein, to prevent the falling of the tree-trunk, their actuator means 9, e.g. a pressurized medium operated cylinder 9a is used to maintain a torque for example in the joint 5d, to keep the supporting means 3a in the desired position. By supplying volume flow at the same time to or from the actuator 9a, it is possible to change the position of the supporting means 3a as well as the position of the horizontal tree-trunk in the substantially vertical (arrow Z) direction. Fig. 2a presents a simple, advantageous embodiment of the actuator means 9. By means of the torque a sufficient force is attained for supporting the weight of the tree-trunk and a sufficient auxiliary force for pressing the tree-trunk against the supporting surface 2d, wherein the position of the tree-trunk can be maintained substantially constant.

Figs. 2a and 2b are reduced skeleton diagrams illustrating the function of the delimbing device 1. Fig. 2b shows the tree-trunk S at the location of the auxiliary delimbing member 4d when seen from the end, and in Fig. 2a at the location of the supporting means 3a when seen from the end. Furthermore, in Figs. 2a and 2b, an axis of coordinates illustrates the position of the horizontally (arrow Y) placed tree-trunk S and the device 1 during the delimbing when compared to the position according to Fig. 1. Fig. 2a also illustrates an advantageous embodiment of the actuator means 9. The control system 10 is in a way known as such connected to different devices for example to transmit signals 13, 14 and 15 between the devices and the control system 10. Typically the signal in question is an analog and/or digital electric signal, which is amplified, filtered, processed and coded according to the requirements of the devices used at a time. The signals 13, 14 and 15 can also be transferred in a wireless manner, for example by utilizing radio waves, wherein the device 1 comprises the necessary transmitters and receivers.

With reference to Fig. 2a, the force effect F₀ exerted on the tree-trunk S by the supporting means can be described by means of an equation k • Fo = Fg + F, in which Fg is the force effect caused by the tree-trunk, which opens the supporting means 3a and is directed downward. The force F is a force effect exerted by the tree-trunk S on the frame structure 2. The variable coefficient k is used for the purpose of taking into account the portion of the force effect F₀ divided between two or more supporting means, as well as the portion of the force effect F₀ which is exerted on the tree-trunk S in a direction perpendicular to the force effect Fg. Other effective forces, such as friction forces, can also be taken into account. The presented dependency is linear, but typically the dependency between the force effects is of the form F = f(Fg, F₀, k), wherein the second force effect F is a function of the first force effect F₀. The coefficient k is affected for example by the mechanical structure of the supporting means 3a, and by the friction factors. Furthermore, a dependency FO = f(p) is effected between the pressure level p and the force effect F₀ of the actuator means 9, wherein the first force effect F₀ is dependent on the pressure p, and the dependency is affected e.g. by the mechanical structure of the supporting means as well as by the length of the tension indicators formed. By means of the presented dependencies, it is thus possible to form the required control algorithm, wherein by adjusting the pressure level p, the second force effect F is also affected. Advantageously, the force effect F affects in a substantially vertical (arrow Z) direction when the tree-trunk S is positioned horizontally. According to the dependency, the force effect F₀ exerted by the supporting means 3a on the tree-trunk S is utilized both for supporting the tree-trunk S (to reverse the force effect Fg) and for producing the desired force effect F. The situation, where the value of the force effect F is zero corresponds to a situation where the force effect F₀ is exactly sufficient for supporting the tree-trunk in its position. Thus, without the force effect, the tree-trunk S can be in contact with the supporting surface 2d or it can be located within a distance E from the supporting surface 2d. By measuring the distance E it is thus also possible to estimate the force effect F (and at the same time the force effect F₀), especially the above-described situation.

The above-presented dependencies and threshold values are stored in the control system 10 of the device 1 to effect the control algorithm of the device 1 , by means of which control algorithm for example the pressure of the actuator means 9, e.g. the cylinder 9a, and the volume flow supplied thereto is adjusted by means of pressure valve means 9c and directional valve means 9b. It is obvious that the motion of the supporting means 3a can also be effected in other ways, for example by means of a torque motor arranged in the articulation 5a. In the control system 10, a computing algorithm is also stored to determine the diameter D of the tree-trunk S on the basis of a dependency described hereinbelow.

The tree-trunk S is pressed against the frame structure 2, and at the same time against the supporting surface 2d, when the supporting means 3a and 3b support the tree-trunk between these means and the frame structure 2. The pressing is due e.g. to the first force effect F₀ exerted by the supporting means 3a on the tree-trunk S. Also when the diameter D and thus also the weight of the tree-trunk S varies during the infeed, the tree-trunk advantageously abuts on the supporting surface 2d to attain the correct diameter. Advantageously, the reference surface 2d and the supporting means 3a are located on the same line in the transverse direction (arrow X) of the tree-trunk, so that the position error caused by the hanging other end of the tree-trunk would not affect the result of the diameter measurement. According to the description above, the supporting surface 2d can also be an integrated auxiliary delimbing member 4d, wherein the tree-trunk S can be placed within a distance from the frame structure 2.

The cylinder 9a, for example the hydraulic cylinder 9a affects the articulation 5a of the supporting means 3a so that the means can be moved in a way known as such. The supporting means 3a and 3b can also be controlled by means of a common cylinder 9a, whose end is coupled in connection with the articulation 5a of the supporting means 3a, with reference to Fig. 1 , to a bracket 5e, and the opposite end is coupled in connection with the articulation 5b of the supporting means 3b. Thus, the position of the supporting means 3a and 3b is controlled by changing the length of one cylinder 9a and the supporting force is controlled by adjusting the pressure level of the cylinder 9a with the actuator means 9. Advantageously, the position of the supporting means 3a is adjusted in such a way that the distance of the upper surface of the tree-trunk S with respect to the supporting surface 2d remains substantially constant, or they are in an immediate contact with each other.

With reference to Fig. 2a, during the delimbing of the tree-trunk S, at least in the articulation 5a of the second supporting means 3a, first sensor means 11 known as such are attached to determine the position of the supporting means 3a. This position is determined e.g. as an angular position α^ of the supporting means 3a with respect to a reference position _r which can vary. By means of this angular position _{1 t} it is also possible to determine the diameter D of the tree-trunk, wherein a particular angular position corresponds to a particular diameter. Advantageously, the angular position is calculatorily directly proportional to the diameter, for example D = α_: • k, and thus D = f( ₁,k), in which k is a coefficient. Thus, the presumption is that the tree-trunk S is located against the supporting surface 2d. In Fig. 2a the supporting surface 2d is presented as a reduced reference level 2d. Thus, it is obvious that when the distance between the tree-trunk and the reference level is increased, the angular position ocι of the supporting means 3a is also changed, wherein the diameter of the tree- trunk S is interpreted to be larger than it actually is. Advantageously, the auxiliary delimbing member 4d and the supporting means 3a and 3b are located close to each other, so that the section in the tree-trunk against which the member 4d is pressed, and the sections against which the supporting means 3a and 3b are pressed would be close to each other. Thus, the position error caused by the hanging other end of the tree-trunk S has a smaller effect on the measuring result.

Further referring to Fig. 2a, the actuator means 9 for controlling the position of the supporting means 3a advantageously comprise a hydraulic cylinder 9a, directional valve means 9b for selecting the direction (arrow L1 and L2) of motion of the piston in the cylinder 9a, pressure valve means 9c, advantageously a proportional pressure valve 9c, to set the pressure level p of the cylinder 9a and directional valve means 9d, advantageously proportional directional valve 9d, to control the volume flow of the cylinder 9a. The actuator means 9 are connected to a pressure and volume flow source P and to a return line T. The actuator means 9 comprise e.g. control electronics known as such to control the same by means of the control and adjustment signal given by the control system 10. In addition, it is obvious that for example the functions of the directional valve means 9b and 9d can be implemented by means of one valve in a way known as such. Moreover, it is obvious that the functions can be implemented with discrete components and together with the pressure valve means 9c for example by means of cartridge valves known as such.

The control system 10 is for example a data processor, such as a computer or programmable logic, which is utilized to control the working machine and which comprises memory means known as such to store the above-described dependencies and the control algorithms. It is obvious that according to the requirements of different embodiments, the control system can be divided in a way known as such into several sub-systems which are connected to each other, but in this description the control system is presented as a single unit for the sake of clarity. The control system 10 is connected to a display 10a for presenting information for the user, to a keyboard 10b for entering the pressure level set by the user into the control system 10, to a control rod 10c for controlling the function of the device 1 , to a speaker 10d for giving signals to the user, to a printer 10f for printing reports and measured data, and advantageously also to a signal light 10e for giving light signals to the user. By means of the devices 10a — 10e it is possible to provide the user with signals and information which can be perceived with senses. The control system 10 is also connected to the first sensor means 11 to determine the diameter D of the tree-trunk S.

According to a preferred embodiment of the invention and with reference to Fig. 2b, the device 1 is also provided with second sensor means 12 to determine the distance E between the tree-trunk and the reference level 2d, advantageously the supporting surface 2d, advantageously in a continuous and stepless manner. With reference to Fig. 2b, the sensor means are arranged in connection with the articulation 5d of the auxiliary delimbing member 4d. These sensor means 12 are used to determine the position of the auxiliary delimbing member 4d as well as the distance of the tree-trunk S from the frame structure, advantageously from its reference level 2d. The auxiliary delimbing member 5d can be pressed in a way known as such against the tree-trunk by means of a spring force or for example by means of pressurized medium operated cylinder (not shown in the drawing), which affects the articulation. This position is determined for example as an angular position ^ of the auxiliary delimbing member with respect to the set reference position β_r, which reference position can vary. By means of this angular position β₁ it is also possible to determine the distance E of the tree-trunk S, wherein a particular angular position corresponds to a particular distance, Advantageously, the angular position is calculatorily directly proportional to the distance, for example E = β₁ • k, and thus E = f(β_1ϊ k), in which k is the coefficient. Advantageously, the distance E is measured preferably in a continuous and stepless manner in order to activate correction measures when necessary. The second sensor means 12 are connected to the control system 10. The articulation of the auxiliary delimbing member 5d can also be arranged in such a way that the motion of the member 5d is substantially linear, advantageously transverse with respect to the tree- trunk S, wherein the sensor means 12 measure the position of the member 5d. Thus, there is a determined dependency between the position and the distance E.

Fig. 3 illustrates the calculation of the diameter D of the tree-trunk S as effected with the supporting means 3a. By means of the angular position o^ and a curve K5 illustrating the above-described dependency, it is possible to determine the diameter D of the tree- trunk. The dependency is advantageously linear, but it can also deviate therefrom. According to a preferred embodiment of the invention, the distance E is utilized to correct the calculated diameter D₁ in such a way that the diameter Di is corrected by means of a shift ΔD, which shift ΔD is proportional to the measured distance E, i.e. ΔD = f(E, D). In addition, the shift can be dependent on the measured value of the diameter D, for example on the value D^ The correction measures are advantageously conducted automatically in the control system 10 of the device 1 , in which the above-described correction algorithm is stored to check and correct the diameter measurement. It is obvious that the correcting calculation can be conducted by means of numerous principles, for example by correcting the angular position o^ which was measured first, thereafter using the curve K5, or by correcting the position of the curve K5 (new corrected curve K6) to determine a new diameter value DY

Advantageously, the auxiliary delimbing member 4d and the supporting means 3a are located close to each other so that the point in the tree- trunk S against which the member 4d is pressed, as well as the point against which the supporting means 3a is pressed would be close to each other. Thus, the measuring error caused by the position error of the tree-trunk S would be as small as possible. Errors are caused in the measurement of the distance E for example by the hanging other end of the tree-trunk S, wherein the longitudinal direction of the tree-trunk S deviates substantially for example from the direction (arrow Y) of the supporting surface 2d.

With reference to Fig. 2c, according to another embodiment of the invention, the second sensor means 12 are arranged in connection with the measuring wheel 15 measuring the length of the tree-trunk S. This measuring wheel 15 is placed in connection with the frame structure 2 by means of an articulation 15a and arranged to follow the upper surface of the tree-trunk S during the delimbing in a way known as such. Advantageously the sensor means 12 are arranged in the articulation 15a to determine the position of the measuring wheel 15a. By means of this angular position it is also possible to determine distance of the tree-trunk S from the supporting surface 2d, wherein a particular angular position corresponds to a particular distance. Advantageously, the angular position is calculatohly directly proportional to the distance and when the distance is determined it is possible to follow the same principles as in connection with the auxiliary delimbing member 4d. Alternatively, the articulation can also be arranged in such a way that the motion of the measuring wheel 15 is substantially linear, advantageously transverse with respect to the tree- trunk S, wherein the position is determined instead of the angular position. Thus, there is a determined dependency between the distance E and the position. Advantageously, the sensor means 12 are arranged in connection to the measuring wheel positioned close to the lower supporting means 3a of Fig. 1 , wherein the measuring error caused by the position error is smaller. Most advantageously, the supporting means 3a measuring the diameter D and the measuring wheel 15 measuring the distance E are substantially on the same line in the transverse direction of the tree-trunk S. In addition, it is also obvious that to measure the distance E, it is also possible to provide the frame structure 2 with a separate roll or a member which follows the upper surface of the tree-trunk S which is directed towards the frame structure 2 during the delimbing. Furthermore, it is obvious that it is also possible to provide the device 1 with sensor means 12 suitable for non- contacting measurement to determine the distance E of the tree-trunk S for example by means of an ultrasonic signal or an electromagnetic radar signal. According to Fig. 2b, the control system 10 is in contact with the second sensor means 12. On the basis of the signal received from the sensor means 12, the control system controls the actuator means 9 according to a preferred embodiment of the invention, wherein when the distance E exceeds a maximum value E₂ set by the user, the position of the supporting means 3a is changed by means of the cylinder 9a, until the distance E attains the maximum value E₂. During the adjustment of the position, the distance E measured with the sensor means 12 is monitored. The gravity (force effect Fg) and the yielding supporting means 3a may have caused the descending of the tree-trunk S in such a low position, that the distance E between the reference level 2d and the upper surface of the tree-trunk S has increased in such a degree that the diameter D calculated on the basis of the angular position of the supporting means 3a is erroneous. It is also possible to feed the minimum value E of the distance E into the control system 10, below which the distance E measured with the sensor means 12 should not be reduced. On the basis of the description above, too small a distance E entails larger friction forces (larger force effects F₀ and F) and drawbacks of prior art caused thereby. When the distance E grows for example beyond the maximum value E₂ set by the user, the position of the cylinder 9a is automatically extended by means of the adjustment until the desired distance E is attained. The maximum value E₂ and the minimum value E^ can be determined for example for each diameter area separately by the user when pressure levels of prior art are used. When the adjustment functions automatically and in a stepless manner, these values can be determined to apply to all diameter sizes. These values can also be determined as an allowed minimum and maximum deviation from the set distance E.

According to a preferred embodiment of the invention, the control system 10 indicates for the user the deviation of the distance E outside set threshold values, for example by means of a light signal, a sound signal, a signal appearing on the display 10a or by means of a signal which can be otherwise perceived with senses. Thereafter the user can set the position of the supporting means 3a with the actuator means 9 and the control system 10 so that the desired distance E of the tree- trunk S would be maintained, or alternatively, that the tree-trunk would cause as small a force effect to the supporting surface 2d as possible. Correspondingly, the user can set e.g. the pressure level on a lower level so that the pressing force F would be lower than the desired one to avoid the above-described drawbacks. The pressing force F can be adjusted for example by setting the distance E as small as possible or into zero and by increasing the pressure level an amount which is estimated to be suitable. The minimum value E₁ or the maximum value E₂ of the distance E is given to the control system 10 for example by means of the keyboard 10b.

According to a preferred embodiment of the invention, the second sensor means 12 are used to control the distance E of the tree-trunk S in such a way that it is only monitored whether the distance E exceeds the determined threshold value. This threshold value, for example a threshold value E₃ is given to the control system 10 by the user. The used threshold value is for example the maximum value E₃ of the distance E, and when this value is exceeded, it indicates that the tree- trunk deviates further off than desired from the supporting surface 2d functioning as a reference level, wherein the diameter measurement is no longer reliable. Correspondingly, it is possible to determine only the minimum value E₄ of the distance E, and if the distance is smaller than this value, it indicates that the pressing forces are too great. In other words, the aim is to keep the tree-trunk S in the desired, advantageously fixed position with respect to the delimbing device 1 and its frame structure 2. The aim is to maintain the position of the tree- trunk S during the delimbing when the diameter and the weight of the tree-trunk varies. It is indicated for the user if the maximum value is exceeded, whereafter it is possible to increase the pressure levels and the diameter measurement can be conducted again. By means of the function the user can set the pressure values on a level by means of which on one hand, the above-described drawbacks are avoided, and on the other hand, a reliable diameter measurement is attained by means of the first sensor means 11. Furthermore, it is obvious that both the user and the control system 10 can take care of the control together and separately. It is also obvious that the user can give the threshold values to the control system 10 in numerous different ways, for example by selecting symbols from menus displayed on the display 10a by means of the control rod 10c. After these symbols have been selected or the different directive numerical values have been entered with the keyboard 10b, the control system 10 takes care of the measurement and control of the distance.

Fig. 4 also illustrates the process of setting the pressure level p of the cylinder 9a for different diameter areas of the tree-trunk S. One diameter area is formed between D1 and D2, in which the pressure level is set into a value p^ For each area it is also possible to set the pressure level separately according to a curve K0, but when one pressure level is changed, the other pressure levels can also change a corresponding amount at the same time. The differences in the pressure levels can be fixed or they can deviate from each other. The control system 10 takes care of changing the pressure level on the basis of the diameter measurement. Heretofore, it was very difficult to determine the correct pressure levels for different conditions, but by means of the present invention it is possible to attain considerable advantages. According to the invention, when the control system 10 indicates the situation of the distance E to the user, the user can reduce the pressure level to comply with a curve K1 or increase the pressure levels to comply with a curve K2. When the control system 10 adjusts the pressure level automatically according to the invention by means of the above-described control algorithm, this pressure level is most advantageously determined in a stepless and continuous manner for each diameter according to a curve K3, wherein a considerably more accurate control is attained when compared to prior art. The pressure level p according to the curve K3 is determined by means of the above-described control algorithm by utilizing the information obtained from the measurement of the distance E. In addition, to maintain the tree-trunk within a desired distance, the volume flow guided to the actuator 9a is adjusted to attain the desired position of the tree-trunk, whereafter the pressure level is maintained in order to retain the position.

According to the invention, the pressure level according to the curve K3 is also adjusted by taking into account the changes in the weight of the tree (also when the diameter remains constant but the density of the tree varies) and thus also the changes in the position of the supporting means 3a. Thus, the pressure according to the curve K3 is constantly adjusted in accordance with the fact that the distance E remains between the above-described minimum and maximum values, below the set maximum value or in an immediate contact with the supporting surface. In the drawing, the curve K3 is shown in a linear manner, but the curve K3 which describes the dependency of the pressure from the diameter can also deviate from the linear one, especially in different conditions.

It is also obvious for anyone skilled in the art that even though the description above illustrates the invention in connection with an advantageous delimbing device, it is obvious that it can also be applied in several other delimbing devices within the scope of the claims.

Claims

Claims:

1. Method in a delimbing device (1), which comprises:

- a frame structure (2), at least one supporting means (3a, 3b, 3c) attached in the frame structure (2) in a movable (5a, 5b, 5c) manner to support the tree-trunk (S), actuator means (9) for controlling the position of the supporting means (3a, 3b, 3c), first sensor means (11) for measuring the diameter (D) of the tree-trunk (S), a control system (10) for controlling at least the actuator means (9),

characterized in that

the distance (E) of the tree-trunk (S) with respect to a set reference level (2d) is monitored by means of second sensor means (12) which are arranged in connection with the device (1) and which are in contact with the control system (10), the distance (E) is compared with a maximum value (E₂, E₃) of the distance (E) set in the control system (10) and/or with a set minimum value (E_{1 (} E₄) of the distance (E) to control at least the actuator means (9) by utilizing the information obtained from the comparison.

2. Method according to claim 1 , characterized in that when the distance exceeds the set maximum value (E₂, E₄) and/or when it is below the set minimum value (E^ E₃), this is indicated to the user in a manner which can be perceived with senses.

3. Method according to claim 1 or 2, characterized in that the control system (10) connected at least to the second sensor means (12) is utilized to adjust the distance (E) by means of a control algorithm stored in the control system (10).

4. Method according to any of the claims 1 to 3, characterized in that the position of at least one supporting means (3a, 3b, 3c) is adjusted to maintain the distance (E) of the tree-trunk (S) below the set maximum value (E2, E3) and/or above the set minimum value (E1 , E4).

5. Method according to any of the claims 1 to 4, characterized in that the distance (E) is measured with second sensor means (12) arranged in connection with a measuring wheel (15) attached in the frame structure (2) in a movable (15a) manner, which measuring wheel (15 ⁾ is arranged to follow the shape of the tree-trunk (S).

6. Method according to any of the claims 1 to 5, characterized in that the distance (E) is measured by means of an auxiliary delimbing member (4d) attached in the frame structure (2) in a movable manner (5d), wherein the second sensor means (12) are arranged in connection with the auxiliary delimbing member (4d).

7. Method according to any of the claims 1 to 6, characterized in that at least the pressure level of the actuator means (9) is adjusted to maintain and adjust the first force effect (F₀) and to maintain the tree- trunk (S) advantageously in an immediate contact with the supporting surface (2d) arranged in the device (1), which first force effect (F₀) is exerted by the supporting means (3a, 3b, 3c) on the tree-trunk (S).

8. Method for measuring the tree-trunk in a delimbing device (1) which comprises:

a frame structure (2), - at least one supporting means (3a, 3b, 3c) attached in the frame structure (2) in a movable (5a, 5b, 5c) manner to support the tree-trunk (S), actuator means (9) for controlling the position of the supporting means (3a, 3b, 3c), - first sensor means (11) for measuring the diameter (D) of the tree-trunk (S), a control system (10) for controlling at least the actuator means (9),

characterized in that

the distance (E) of the tree-trunk (S) with respect to a set reference level (2d) is monitored preferably in a continuous manner by means of second sensor means (12) which are arranged in connection with the device (1) and coupled to the control system (10), the information obtained from the measurement of the diameter (D) of the tree-trunk is corrected on the basis of the information obtained from the measurement of the distance (E) by means of a correction algorithm, which information and correction algorithm is stored in the control system (10).

9. Delimbing device (1) which comprises:

- a frame structure (2), at least one supporting means (3a, 3b, 3c) attached in the frame structure (2) in a movable (5a, 5b, 5c) manner to support the tree-trunk (S) and to exert a first force effect (F₀) on the tree-trunk (S), - actuator means (9) for controlling the position of the supporting means (3a, 3b, 3c) to maintain the first force effect (Fo) exerted by the supporting means (3a, 3b, 3c) on the tree-trunk (S), first sensor means (11) for measuring the diameter (D) of the tree-trunk (S), a control system (10) for controlling at least the actuator means (9),

characterized in that

the delimbing device (1) also comprises second sensor means (12) arranged in connection with the device (1) and coupled to the control system (10), to measure the distance (E) of the tree-trunk (S) with respect to a set reference level (2d) , and

- in the control system (10) a set maximum value (E₂, E₃) of the distance (E) and/or a set minimum value (E_t, E₄) are stored to compare the distance with these values (E^ E₂, E₃, E₄) and to change the position of the supporting means (3a, 3b, 3c) with the actuator means (9) by utilizing the information obtained from the comparison.

10. Delimbing device according to claim 9, characterized in that in connection with the measuring wheel (15) fixed in the frame structure (2) in a movable manner (15a), second sensor means (12) are arranged to measure the distance (E), which measuring wheel (15) is arranged to follow the shape of the tree-trunk (S).

11. Delimbing device according to claim 9, characterized in that in connection with the measuring wheel (15) fixed in the frame structure (2) in a movable manner (5d), second sensor means are arranged to measure the distance (E), wherein the sensor means (12) are arranged in connection with the auxiliary delimbing member (4d).

12. Delimbing device according to any of the claims 9 to 11 , characterized in that in the control system (10) a control algorithm is stored to adjust the distance (E) by means of the position of the supporting means (3a, 3b, 3c) and on the basis of the information obtained at least from the second sensor means (12).