Woodworking – Process – Timber harvesting or processing
Reexamination Certificate
2001-03-09
2001-11-20
Bray, W Donald (Department: 3725)
Woodworking
Process
Timber harvesting or processing
C144S004100, C144S024130, C144S338000, C144S357000
Reexamination Certificate
active
06318425
ABSTRACT:
The invention relates to a method in a delimbing device according to the preamble of claim
1
. The invention also relates to a delimbing device according to the preamble of claim
7
.
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 immovably in the frame structure. 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 U.S. Pat. No. 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, wherein the position of the tree in the delimbing device is changed.
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
Bray W Donald
Quarles & Brady LLP
Timberjack OY
LandOfFree
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