Woodworking – Special-work machine – Tree felling
Patent
1993-11-29
1995-08-29
Bray, W. Donald
Woodworking
Special-work machine
Tree felling
303795, 83928, 144 3D, 144336, A01G 2308
Patent
active
054451973
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an arrangement in a tree-processing assembly of the type comprising a frame which is connectible to the tip of a crane via a rotator and with which a pivotable carrier is hingedly connected, said carrier comprising at least one set of grapples for gripping and holding a log, and a cutting tool, such as a chain-saw guide bar, attached to a lower part of said carrier.
Such tree-processing assemblies can be divided into two different basic types, e.g. so-called "harvesters" and "pure felling" assemblies. A one-grip type harvester comprises, in addition to grapples and a cutting tool, a number of limbing knives and at least one set of feed rolls by means of which the felled tree held by the grapples, can be longitudinally fed relative to the carrier and thus be separated from the limbs. By means of such harvesters, a tree can thus be felled, delimbed and cut to suitable lengths. However, in conventional felling assemblies, there are, no feed rolls, and therefore such assemblies can only cut the tree at the root, without delimbing it.
BACKGROUND OF THE INVENTION
In modern forestry, tree stands are in most cases thinned by means of e.g. "one-grip" harvesters. A frequent problem in such thinning is caused by the thicket or shrub layer which is often found adjacent the trees which are to be thinned and cut. Such thicket normally grows around the lower part of the tree to be cut, thus preventing a clear view by the person who operates the harvester from a driving-cab located a considerable distance from the tree. Besides blocking the operator's view, the thicket also causes problems by easily finding its way between the the trunk and the saw chain mounted on the guide bar of the harvester, which serves as a cutting tool. As a result, the chain may slip or jam and, consequently, lose its capacity of effectively cutting the trunk. To eliminate the problems caused by thicket surrounding the tree, in practice there is usually a special operator who manually cleans the tree stand from the shrub layer by means of a conventional bush saw, before the actual thinning is carried out. However, this work is costly and involves a number of drawbacks. One drawback is that the cleaning operator does not know in advance which direction the harvester will be moving towards the tree to be thinned. Thus the operator must remove all the thicket in a 360.degree. sector around the tree. Removing substantially all the thicket in this manner while leaving completely bare surfaces around the tree is contrary to recent environmental protection practices which recommend a certain amount of shrub layer in a growing forest, to create a favourable environment for forest animals. Such clear-cleaning involves extensive work which takes much time and thus is expensive. In practice, the cost for manual thicket-cleaning alone is estimated at 15-20% of the total thinning cost. A further problem relates to the technical planning, particularly for large forest owners with a large number of scattered stands. Thus, it is extremely difficult to plan the cleaning operator's work to coordinate efficiently with the thinning operation.
BRIEF DESCRIPTION OF THE INVENTION
The present invention aims at overcoming the above-mentioned drawbacks by eliminating the need for manual cleaning and for permitting the removal, as required, of thicket and shrub layer which may be obstructing the thinning operation. According to the invention, this is achieved by providing on the lower part of the carrier of a tree-processing assembly of the above-mentioned type, there is mounted a rotary saw blade which is pivotably movable between an inactive position and an active position in which it can cut shrub layers and/or small trees.
According to a preferred embodiment of the invention, the saw blade is dismountably arranged on a shaft which is rotatably mounted and connected to a hydraulic motor, which in turn, is arranged on a support member. The support member may be a plate, which in turn is articulated to the low
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