Woodworking – Special-work machine – Tree delimbing
Patent
1999-01-15
2000-05-23
Bray, W. Donald
Woodworking
Special-work machine
Tree delimbing
144247, 144343, A01G 23095
Patent
active
060655135
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the grapple structure of a tree harvesting machine, harvester, to be driven on a terrain, the grapple being used for felling, delimbing and cutting the tree, and particularly for gripping the trunk of the tree.
Trees to be felled, delimbed and cut vary to a great extent in their diameters, knottiness and body shape, and the diameter of a single trunk can be about half a meter in the lower part of the stem and only 5 cm at the crown end. The machine part, grapple, which is capable of felling and delimbing, should be relatively massive, wherein it can also easily damage the tree to be felled. This applies also to those means of the grapple which are used for delimbing. Further, high demands are set on the delimbing means by the variety of knots, their thickness, shape of butt, and number. Moreover, the delimbing blades should follow precisely the variations in thickness of the trunk.
This invention presents a method for evening out the clamping force of the tree feeding means and the delimbing means against the trunk and for providing said means with a degree of flexibility at quick changes in trunk diameter. This results in obvious advantages in the use as well as the design of the means.
The grapple of the harvester, fixed to the crane part of a terrain vehicle, is composed of tree feeding means, such as rollers, fixed to the grapple support structure, as well as of tree delimbing means, the delimbing blades. The grapple includes also a tree cross-cutting device, the means related to measuring the tree, as well as the driving and actuating apparatus of the said means, which are usually hydraulic motors or cylinders with the related control devices. The equipment related to positioning the grapple for tree felling, delimbing and manipulation will not be discussed in this specification.
The grapple of the harvester has two operating positions when used in a forest. For felling the tree, the grapple is in a vertical position, wherein the grapple grips the trunk primarily with the feeding means. These means can be rollers, chain track constructions wound around two rollers, or the like. Also the delimbing means can be helpful when fixing the grapple to the trunk. The clamping motion of both against the trunk is usually achieved with hydraulic cylinders. The feeding movement of the feeding means is usually achieved with hydraulic motors.
For delimbing the trunk and cutting it to lengths, the feeding means feed the trunk forward starting from its bottom and the movement is continued towards the crown. The grapple is stopped when a trunk part of a certain length has been measured, and the trunk is cut by the cutting means placed in the grapple. This is continued until the trunk is cut into suitable pieces. In the same connection, when the trunk moves through a circle formed by the delimbing blades fixed in the grapple, the blades cut the knots off the trunk. The trunk transfer movement is very fast, and thus both the feeding means and the delimbing means must give way to the trunk passed between them according to the changes in the diameter and roughness of the trunk.
Particularly when the tree feeding rate, i.e. the rate at which the trunk is moved by the feeding means, is high, the problem arises how to achieve sufficiently fast pressure control of the hydraulics in the hydraulic cylinders generating the compression in order to avoid extra loads on the transport means and the delimbing means. This is achieved by using pressure control valves with high flow-through capacity and precise control properties as well as pipe systems with a larger diameter. Also the rollers of the feeding means must be equipped with a thicker elastic layer of (for example) rubber.
Swedish Published Specification No. 467 102 discloses a basic grapple solution having track chains as the feeding means, their clamping movement as well as the delimbing means of the same apparatus and their blades being controlled by hydraulic cylinders. The track chains of the feeding means are equipped with rubber elements
REFERENCES:
patent: 3724518 (1973-04-01), Zehavi et al.
patent: 4194542 (1980-03-01), Eriksson
patent: 4515192 (1985-05-01), Eriksson
patent: 4662413 (1987-05-01), Bater
patent: 5186227 (1993-02-01), Eriksson
Bray W. Donald
Plustech Oy
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