Patent ID: 12245554

First of all, reference is made toFIG.1, which shows a perspective view of a sawing and gripping unit according to the invention with its attachment area1for attachment to an extension arm (not visible inFIGS.1-5). The sawing and gripper unit comprises a sawing unit2and a gripper unit3.

In the exemplary embodiment shown, the gripper unit3has two pairs of grippers4,5of two gripper arms4a,4b,5a,5bfor a tree trunk, which can be pivoted about gripper pivot axes G1, G2to each other, wherein the gripper arms4b,5bare concealed by the visible parts of the gripper unit3, and the sawing unit2has a pivot drive, arranged in a saw box6, for a cutting element, arranged such that it can be pivoted out of the saw box6, for cutting through the tree trunk, which cutting element is designed as a chain saw. The attachment area1establishes the connection to an extension arm not shown inFIGS.1-5, for example via a rotating mechanism by means of which the sawing and gripper unit can be rotated relative to the extension arm and which comprises a gripper-side rotating part arranged on the gripper unit3and an extension-arm-side rotating part arranged on the extension arm. The movements of the extension arm are thus transmitted directly to the sawing and gripper unit via the rotating mechanism. The rotating mechanism can also be used to effect a rotational movement of the sawing and gripper unit relative to the extension arm. Hydraulic lines (not shown inFIGS.1to5) for the pairs of grippers4,5extend on or in the attachment area1, which are operated by an operating pulpit and cause the pairs of grippers4,5to close and open. When closing, the gripper pairs4,5swing towards each other in a pincer-like manner, and when opening they move away from each other.

The saw box6is designed in a conventional manner and opens in the direction in which the pairs of grippers4,5also open. When pivoting out of the saw box6, the cutting element thus traverses in a known manner an area located below the gripper arms4a,4b,5a,5bfor cutting through a tree trunk. The sawing unit2is arranged on the gripper unit3so as to be pivotable about a pivot axis S, a suspension of the sawing unit2relative to the gripper unit3being realized with the aid of a spring element7so as to be movable about the pivot axis S (see alsoFIG.2). The spring constant of the spring element7is selected in such a way that, on the one hand, safe cutting guidance is ensured, but, on the other hand, sufficient flexibility of the suspension is ensured when loads are applied to the chain saw. The pivot axis S is preferably arranged below the lowest pair of grippers5and perpendicular to their gripper pivot axes G1, G2. When the gripper pivot axes G1, G2are arranged vertically for gripping around a tree trunk, the pivot axis S of the saw box6is therefore aligned horizontally so that the saw box6can be tilted downward. The pivot axis S further represents a bearing via which the saw box6is hinged to the gripper unit3, as shown inFIGS.2-5.

In addition to the spring unit7, a piston-cylinder unit8is provided, wherein the spring element7and the piston-cylinder unit8are arranged on the side of the gripper unit3facing away from the gripper arms4a,4b,5a,5b. In the embodiment shown, the spring element7is designed as a helical compression spring, which is arranged essentially parallel to the longitudinal axis of the piston-cylinder unit8. The piston-cylinder unit8thus acts essentially along the effective axis of the helical compression spring. The spring element7and the piston rod of the piston-cylinder unit8are attached to a linkage area9, which is integrally formed on or attached to the saw box6and kinematically forms a two-armed lever with the saw box6about the pivot axis S, wherein the saw box6forms a first lever arm and the linkage area9forms a second lever arm. In the exemplary embodiment shown, the linkage area9is designed in the form of plate-shaped linkage levers9a,9bprojecting from the saw box6, to which the spring element7and the piston-cylinder unit8are attached in an articulated manner. The linkage lever9aprovided for fastening the piston rod of the piston-cylinder unit8has an elongated hole10(see in particularFIGS.3a,4a,5a) for ensuring a free movement space for the saw box6. The spring element7is articulated to the linkage lever9bassociated with it with the aid of a pivot bearing11, which ensures mobility of the spring element7about an axis of rotation parallel to the pivot axis S. On the side facing away from the linkage area9, the spring element7and the piston-cylinder unit8are likewise attached to the gripper unit3so that they can move about axes of rotation parallel to the pivot axis S. As shown inFIGS.3-5, the spring element7and the piston-cylinder unit8are mounted on the gripper unit3on the side facing away from the linkage area9in such a way that forces can be dissipated via the gripper unit3.

The spring element7and the piston-cylinder unit8thus form, together with the bearing of the pivot axis S, a suspension for the saw box6, wherein the spring element7defines, by means of a restoring torque about the pivot axis S in its equilibrium position, a predetermined cutting position of the saw box6with a cutting plane of the cutting element assigned to it, into which the cutting element is returned with the aid of the spring element7after deflections due to external loads. Since the saw box6is held with play in its cutting position relative to the piston-cylinder unit8with the aid of the elongated hole10and can thus move relative to the piston rod within the limits of the elongated hole10, mobility of the saw box6and the cutting element is ensured even when the piston rod is inactive and thus motionless.

By activating the piston-cylinder unit8, the saw box6can be actively and controllably tilted by the piston-cylinder unit8about the pivot axis S into its inclined position, to which an inclined plane of the cutting element tilted with respect to the cutting plane is assigned, by overcoming the restoring torque of the spring element7and on reaching the limit of the elongated hole, wherein the spring element7is co-pressed. In this way, the cutting element can be tilted into an inclined plane at a distance from the tree trunk in order to avoid or remove blockages.

The operation and advantages of the invention will be described in more detail below.

FIG.1first shows a configuration in which a tree trunk can be encompassed, wherein the sawing and gripper unit is oriented with substantially vertical gripper pivot axes G1, G2of the pairs of grippers4,5and of the pivot drive of the chain saw. The cutting plane of the chain saw is oriented substantially horizontally. The axis of rotation of the rotating mechanism is also oriented substantially horizontally in this positioning. During the cutting operation of the chain saw, the rotating mechanism is locked and does not perform any rotary movements, so that the tree trunk is largely fixed relative to the extension arm during the cutting operation of the chain saw. As mentioned, the pairs of grippers4,5serve to enclose a tree trunk to be cut, wherein they fix the tree trunk in the closed state. When the pairs of grippers4,5are closed, the chain saw is inside the saw box6and thus in an inactive position. After the pairs of grippers4,5have been closed and the tree trunk is thus fixed, the pivot drive for the chain saw can be activated from the operating pulpit, wherein on the one hand the rotating movement of the cutting chain is started, and on the other hand the chain saw is pivoted out of the saw box6and pivoted in the direction of the tree trunk to be cut. The rotating cutting chain of the chain saw thus enters the tree trunk and cuts through it. In order to be able to deposit the severed tree trunk, the locking of the rotating mechanism is released and the rotating mechanism is actuated in such a way that the sawing and gripper unit is pivoted into a position in which the severed tree trunk is aligned substantially horizontally and can be deposited on the ground.

However, cutting through a tree trunk with the help of a chain saw is not without problems, as described at the beginning. In particular, due to the increasingly acting dead weight of the tree trunk, the guide bar and the rotating cutting chain of the chain saw can block. Although blocking of the chain saw could be avoided by appropriate control of the extension arm, this is hardly successful in practice. In particular, when the chain saw exits after completely cutting through the tree trunk, impact-like loads become effective that cannot be absorbed quickly enough by controlling the extension arm.

These loads acting on the chain saw are reduced by the fact that the sawing unit2is arranged on the gripper unit3so as to be pivotable about the pivot axis S, and a suspension of the sawing unit2relative to the gripper unit3that is movable about the pivot axis S is realized with the aid of the spring element7. This basic position is shown inFIGS.3aand3b. In this case, the spring element7defines a predetermined cutting position of the saw box6in its equilibrium position with a substantially horizontal cutting plane of the cutting element assigned to it via a restoring torque about the pivot axis S. The piston-cylinder unit8initially remains inactive. However, since the saw box6is held with clearance in its cutting position relative to the piston-cylinder unit8with the aid of the elongated hole10and can thus move relative to the piston rod within the limits of the elongated hole10, mobility of the saw box6and the cutting element about the pivot axis S is ensured even when the piston rod is inactive and thus unmoved.

Loads acting on the cutting element during the cutting of a tree trunk are reduced with this bearing, since they can be cushioned about the pivot axis S with the aid of the spring element7, as shown inFIGS.4aand4b. InFIGS.4aand4b, a load is represented in the form of an external force K, which would in itself place a heavy load on the saw box6and the cutting element. However, the saw box6can spring down in the direction of the drawn arrow in the event of such an external load due to the spring bearing around the pivot axis S, whereby the loads on the cutting element can be reduced. The spring element7exerts a restoring torque about the pivot axis S on the saw box6and the cutting element, which returns them to the cutting position with an essentially horizontal cutting plane after deflections caused by external loads.

In order to avoid blockages of the cutting element, for example due to a slipped tree trunk, the piston-cylinder unit8can additionally be activated, as shown inFIGS.5aand5n.

After activation of the piston-cylinder unit8in the direction of the arrow shown upwards inFIG.5a, the saw box6can be pivoted in the direction of the arrow facing downwards in overcoming the restoring torque of the spring element7into an inclined position relative to the cutting position, to which a plane of inclination of the cutting element tilted relative to the cutting plane is assigned, wherein the spring element7is compressed. In this way, the cutting element can be tilted to an inclined plane spaced from the tree trunk in order to avoid or remove blockages. Subsequently, the piston-cylinder unit8can be returned to its initial position in order to return the saw box6to its cutting position.

With the aid of the invention, loads on the cutting element during the cutting of a tree trunk can thus be reduced and, in particular, functional impairments due to blockages of the cutting element can be avoided.