Woodworking – Process – Timber harvesting or processing
Reexamination Certificate
1999-09-15
2001-09-18
Bray, W. Donald (Department: 3725)
Woodworking
Process
Timber harvesting or processing
C144S024130, C144S004100, C144S356000, C144S382000
Reexamination Certificate
active
06289957
ABSTRACT:
The invention relates to a control method of a tree harvesting machine which is presented in the preamble of the appended claim
1
. The invention relates also to a control apparatus which is of the type presented in the preamble of the appended claim
5
.
The invention is intended for use in forest machines movable in the terrain, such as grapple harvesters. Such forest machines have a tree manipulating part, a grapple, at the end of an arm arranged movable in a body. The part comprises a cross-cutting saw for cutting off a tree and cutting it into lengths of determined size, as well as a tree feeding device for feeding the cut tree forward. Such forest machines are presented e.g. in European patent 428530, Finnish patent 79927 and U.S. Pat. No. 4,742,854.
Upon starting the processing of trees cut with such machines, the butt end of the tree is between feeding means, such as rolls or wheels, and it is also supported by delimbing blades. The feeding device pushes the stem past the cross-cutting saw a distance corresponding to the cutting length. Particularly with thick stems, the weight of the stem becomes so high that it tends to bend the tree at the cutting point so that the cutting track does not become even and damage may be caused in the tree, in the worst case cracks.
In a cutting situation, it is not possible to support the tree on the butt end side, because the cross-cutting saw is the lowest means in the tree processing part, i.e. the means closest to the butt end at the cutting point, and it has to fit lowest in the cutting off of the tree, i.e. as close to the ground as possible.
Swedish published specification 409431 presents a device for cutting a felled tree, in which the saw swinging from below upwards during the cutting movement is followed by a wedge means to avoid cracks in the remaining part of the tree, as well as stucking of the saw. In the swinging motion from above downwards, which is recommended for smaller stems, no auxiliary means are used to prevent cracks. The cutting device in question is not intended for a tree harvesting machine movable in the terrain.
It is an aim of the invention to present a method for eliminating said drawback and for avoiding quality problems to a maximum extent in timber intended for high-quality wood products. For achieving this aim, the method according to the invention is primarily characterized in what will be presented in the characterizing part of the appended claim
1
. An essential aspect in the invention is to move the part supporting the tree at the very moment of cutting to compensate for the force tending to bend the tree. This involves a momentary movement produced by control automatics and timed precisely at the moment of action of the cross-cutting saw, to make the bending moment at the time of cutting as close to zero as possible, or at least considerably smaller than without the movement. It is important that the function is performed automatically by means of the control automatics of the machine at the right moment in the cutting sequence of the tree stem without the operator needing to produce it by his own special manual measures by manoeuvring respective actuators. Other features of the invention will be presented in the appended dependent claims
2
to
4
.
The control apparatus of a tree harvesting machine for applying the invention is, in turn, characterized in what will be presented in the characterizing part of the appended claim
5
. The operations of the invention can be implemented with an apparatus in which the control means of the cross-cutting saw are connected in a suitable way to the actuators responsible for the movements of the part supporting the tree.
Other advantageous features of the apparatus will be presented in the appended dependent claims
6
and
7
.
REFERENCES:
patent: 3554249 (1971-01-01), Arnelo
patent: 4250935 (1981-02-01), Helgesson et al.
patent: 4513799 (1985-04-01), Lindblom et al.
patent: 450356 (1988-09-01), None
http://www.orebro.asdo.se/tidning/ti_sprik.htm, “Bergslaghen Skog & Trä 4/97” Published in 1997 (with translation).
Ulf Hallonborg, Dag Myhrman, Publication “Skogforsk-Nytt, Feb. 1997” Published in 1997 (with translation).
Bray W. Donald
Plustech Oy
Quarles & Brady LLP
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