Woodworking – Bark rosser – Including means to simultaneously rotate and advance log
Reexamination Certificate
1999-07-28
2001-02-20
Bray, W. Donald (Department: 3725)
Woodworking
Bark rosser
Including means to simultaneously rotate and advance log
C144S208100, C144S341000
Reexamination Certificate
active
06189583
ABSTRACT:
The present invention relates to an apparatus for removing barks from a wood- and bark-containing log flow to be fed into the apparatus.
In view of the quality of pulp, it is important that the amount of barks ending up in chipping along with tree trunks be kept as small as possible. Separation the bark off the surface of tree trunks is usually carried out in a barking drum, wherein the relative motion and attrition of tree trunks result in the bark peeling off the surface of tree trunks. The loose finely crushed bark falls mostly through the bark openings of the drum onto a bark conveyor set below the drum. However, the loose bark removed in the form of long strips or large sheets strives to come out of the discharge end of the barking drum along with tree trunks. Such hard-to-bark trees include several species of hardwood, such as eucalyptus, acacia, hickory, and birch.
If the discharge end of a barking drum turns out bark entangled with logs and in the form of individual strips or bark balls (bark balls in this context refer to a heap consisting of more or less intertwined barks, possibly containing also pieces of wood, slivers or the like), the removal of most of said bark is endeavoured prior to chipping or other such treatment of the logs. Partial separation of bark can be effected by means of a purposely designed roller system. However, the bark balls and some of the long bark strips are difficult to remove by means of a roller system; a moderately close-spaced, wood (pieces of wood) saving roller system tends to leave almost the entire bark ball and some of the loose barks in the log flow, whereas a wide-spaced roller system removes most of the loose barks and even some of the bark balls but results simultaneously major losses of wood.
The Applicant's earlier patent FI 76511 discloses an apparatusas described above for removing barks. Operation of the apparatus is based on a roller system, including a spiked rollers and smooth-surface rollers, which are vertically staggered relative to each other and wherein, furthermore, a smooth roller set between two spiked upper rollers is located closer to the upstream spiked roller than to the downstream spiked roller for dropping the barks through this wider gap onto a conveyor below. The apparatus is primarily intended for the removal of short barks. The removal of material containing long barks and especially bark balls is more difficult to handle with this type of apparatus.
An object of the invention is to provide an apparatus of the above type, which is capable of removing various barks, especially long barks and bark balls from a log flow containing wood and bark.
According to the invention, this object is achieved in such a manner that and an apparatus of the invention is characterized in that the appratus includes a number of bark separation units, each of said bark separation units comprising an aggregate of a toothed disc mounted on a disc shaft and a smooth-surface disc mounted on a second disc shaft, that the disc shafts are set crosswise relative to a feeding direction A applied to the log flow by the toothed disc upon the rotation thereof and at a distance from each other, and that the toothed disc and the substantially smooth-surface disc of a bark separation unit are set in a staggered fashion relative to each other in the axial direction of the disc shafts.
In the apparatus of the invention, the toothed discs provide a log flow with a momentum in the advancing direction of a tooth and simultaneously the teeth apply to the log a vibration effect, whereby the short barks or those extending radially of the discs fall directly in between the discs and further onto a conveyor or the like below. The forward motion of barks or bits of bark advancing in a crosswise position on top of the discs decelerates at a smooth-surface disc, whereby the teeth of a toothed disc, especially if designed as take-up teeth, force the barks—possibly one bit at a time—through a gap between the smooth-surface disc and the toothed disc down onto a bark conveyor or the like.
In a preferred embodiment of the invention, the configuration is such that the disc shaft carries a number of discs spaced from each other in the axial direction of the disc shaft, said discs being selected from a group comprising toothed discs and substantially smooth-surface discs. Thus, in the apparatus of the invention, the disc shaft may carry a number of toothed discs only or a number of smooth-surface discs only or the disc shaft may be provided both with a desired number of toothed discs and a desired number of smooth-surface discs.
In one preferred embodiment of the invention, the configuration is such that the discs carried by two disc shafts successive in said feeding direction A are set overlappingly relative to each other in the radial direction of the disc shafts. The radial overlap can be varied for influencing on the efficiency of bark ramoval. The lesser the overlap, or especially if there is no overlap at all, the more certain is the removal of barks. At the same time, however, this results in increased losses of timber since wood material will also have an easier discharge passage along with barks.
In order to intensify and facilitate the removal of barks, the arrangement in one preferred embodiment of the invention is such that the smooth-surface discs are adapted to have a peripheral speed which is lower than that of the toothed discs. If necessary, the arrangement may be such that the smooth-surface discs are adapted to rotate in the opposite direction relative to the toothed discs. In order to achieve the best possible result, the arrangement may be such that the smooth-surface discs and the toothed discs have a relative peripheral speed difference which is adapted to be variable. By virtue of these measures, the advancing movement of bark can be momentarily decelerated at a smooth-surface disc, whereby the teeth of said toothed discs have more time to work for the removal of barks and for dropping the same onto a conveyor set below the discs.
In order to intensify the vibration effect produced by the toothed discs, the configuration of the invention is such that the teeth of adjacent toothed discs mounted on a common disc shaft are offset relative to each other. Thus, the teeth of a toothed disc shaft are readily capable of gripping resilient barks, yet incapable of gripping rigid pieces of wood so as to break the pieces of wood and force the removal of the same from the apparatus through a gap between the disc shafts.
In one preferred embodiment of the invention, the configuration is such that the width of the toothed discs as measured in the axial direction of the disc shaft exceeds the corresponding width of the smooth-surface discs. Among other things, this contributes to the deceleration of the advancing movement of bark at a smooth-surface disc, whereby the toothed discs are capable of taking the bark more effectively through a gap between the disc shaft carrying toothed discs and the disc shaft carrying smooth-surface discs onto a conveyor or the like set therebelow.
The log flow may be adapted to advance into the apparatus itself at an angle, which is within the range of about 0° -about 90° relative to the lengthwise direction of the disc shaft.
The invention will now be described in more detail by way of example with reference made to the accompanying drawings, wherein:
FIG. 1
is a schematic plan view of an apparatus according to one embodiment of the invention.
FIG. 2
shows a section along a line II—II in FIG.
1
.
FIG. 3
is an end view of a disc shaft fitted with toothed discs in the direction of an arrow III in FIG.
1
.
FIG. 4
is an end view of an apparatus according to one embodiment of the invention in the direction of an arrow IV in FIG.
1
.
FIG. 5
shows a section similar to
FIG. 2
of an apparatus according to a second embodiment of the invention.
REFERENCES:
patent: 1319935 (1919-10-01), Thorne
patent: 1549855 (1925-08-01), Cote
patent: 1966153 (1934-07-01), Thorne
patent: 2125529 (1938-08-01), Ullgren
patent: 2137
Hannimaki Ari
Kokko Pekka
Pitkåkangas Jaakko
Alix Yale & Ristas, LLP
Andritz-Patentverwaltungs-GmbH
Bray W. Donald
LandOfFree
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