Woodworking – Special-work machine – Tree delimbing
Reexamination Certificate
2000-04-11
2001-03-20
Bray, W. Donald (Department: 3725)
Woodworking
Special-work machine
Tree delimbing
C144S004100, C144S245200, C144S338000, C144S343000, C198S626100, C198S692000
Reexamination Certificate
active
06202719
ABSTRACT:
The present invention relates to a timber harvester, which includes two feeder devices jointed opposite one another, stripping blades, and a cutting device, and in which the frame of the feeder device is set on jointed arms. The invention particularly relates to the feeder device used in the timber harvester, which includes a roller chain of two or more rows of links set to travel around a drive cog, a turning device, and slide guides, which extend over the major length of the adhesion side between the drive cog and the turning device.
Patent publications WO 85/05589 (Ketonen,=EP 218 584), FI 84009, and FI 83831 describe feeder track devices intended for timber harvesters and especially for grab harvesters. Years of experience have shown that the best of these devices is the feeder device according to the Wo publication, in which a roller chain, which is supported by slide guides at least on the adhesion side, is used as a crawler track. It is preferable to use a three-row roller chain, in which the middle row of chain links is staggered in relation to the outer rows. In addition, a drive cog driving only one row of links, the centre row, is used, so that the outer slide guides extend to the line of the axle of the drive cog and preferably to the area where the crawler track turns. This solution directs most of the point stresses of the crawler track directly onto the slide guides. Over the short transitional area, the outer rows of links between the slide guides and the drive cog carry the central row of links.
The feeder track device according to the WO publication is jointed so that it can twist slightly according to the direction of the feed of the tree if the tree is not fed exactly parallel to the harvester. The moment caused by the feeding movement increases the loading pressure in the exit end.
Generally, the turning member acting against the drive cog is an idler wheel, but alternatively simple slide surfaces can act as a turning member.
Traditionally, the feeder track device has competed with feeder roller devices. The crawler track, which corresponds to an infinitely large wheel, by means of its long adhesion surface, uses a small surface pressure to create a reliable and stable contact with the tree. The roller's problem, despite various surface members that improve adhesion, is often a point-like contact, which easily gives rise to random, indiscriminate damage to the surface of the timber. Chains and surface plates used in rollers initially improve adhesion, but become clogged with material from bark torn from the timber. This kind of clogging is unlikely with a crawler track, because the variation in the curvature of the track as it rotates cleans it effectively.
This invention is intended to simplify both a timber harvester using a feed track and the feed track itself. A timber harvester according to the invention is characterized in terms of the accompanying claim
1
, while the improved feeder track is characterized in terms of claim
6
. In a feeder track according to the invention, the infinite radius of curvature of the earlier track is set to a finite value, which alters the nature of the track. A crawler track according to the invention behaves partly according to the radius of curvature of the point of adhesion, i.e. like a large diameter feed roller, but in this case the track cleans itself, because the radius of curvature varies greatly during a single rotation. In addition, a small amount at the drive cog is sufficient to drive the crawler track. In any event, the curvature is so great that the adhesion surface becomes quite long. A feeder track according to the invention is preferably rigidly attached to its articulated driving arm. The curvature of the feeder track permits small differences in the angle of the feed of the tree. A curved and especially convex construction concentrates the greatest load at the nip point, where the slide surfaces act effectively. In the vicinity of the drive cog and correspondingly the idler wheel, there is no longer any load.
REFERENCES:
patent: 4883159 (1989-11-01), Ketonen
patent: 502863 (1920-05-01), None
patent: 767764 (1934-07-01), None
patent: 391628 (1972-01-01), None
patent: WO 8505589 (1985-12-01), None
Bray W. Donald
Kilpatrick & Stockton
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