Woodworking – Bark rosser – Drum or tank
Reissue Patent
1994-08-23
2001-12-04
Bray, W. Donald (Department: 3725)
Woodworking
Bark rosser
Drum or tank
C144S242100, C144S250170, C144S246100, C144S341000, C198S624000, C198S836100
Reissue Patent
active
RE037460
ABSTRACT:
The present invention relates to a method and apparatus for debarking logs. More particularly, the invention hod and apparatus for debarking tree length logs for efficient high yield further processing to obtain high grade wood chips, or good lumber of substantial lengths, but which can also be used to debark logs of virtually any length.
BACKGROUND OF THE INVENTION
The most efficient and economical way to debark logs is with the horizontal drum debarker. The drum debarker has a continuously rotating drum which rotates groups of logs so they rub against each other to remove the bark from the logs without any appreciable wear to the drum. To obtain good debarking efficiency, at least several logs must be in the same axial region of the drum, so they can rub against each other to remove the bark. The logs are usually fed into the drum in a continuous stream of groups of logs from an elevated curved hopper at one end of the drum and slide by gravity into the drum.
A hopper dimensioned to feed groups of relatively short logs of up to perhaps fifteen feet in length into the drum, does not work well with longer logs. Very long logs such as tree length logs, tend to jam and are bent by the hopper and drum when their lower ends enter the drum and the logs begin to rotate while their upper ends are still above the hopper inlet. Long logs in this position are rotated by the drum and are often damaged by rubbing against the hopper inlet, and the resultant reverse bending sometimes causes such long logs to break.
While it may be possible to efficiently debark tree length logs by using a much larger hopper, such a hopper would be very high and difficult to feed logs into, the hopper would be quite expensive, and shorter logs would not feed efficiently through such a larger hopper.
Thus, is has been necessary in the past to cut or slash tree length logs to shorter debarking length, before feeding the logs into the hopper. However, the saw used for cutting or slashing logs is costly to install and maintain, and there is some kerf i.e., blade width loss when logs are cut with a saw.
Other disadvantages of shorter logs is that there are more ends, which are subject to brooming, shorter logs often tumble in the debarking drum which causes more end damage, and shorter logs are less efficiently chipped, and yield less usable lumber.
On the other hand, debarked tree length logs provide a higher yield of usable lumber, and a higher yield of high quality uniform size chips for pulp can also be obtained from debarked tree length logs.
The problem has been that there was previously no efficient reliable way to debark tree length logs with a drum barker.
In addition to directing relatively short logs into the drum, the hopper for such logs performs a containment function on the logs entering the drum. As the leading ends of the logs enter the continuously rotating drum and engage the inside of the drum, the logs begin to rotate while they are partly in the hopper. Such rotation sometimes causes additional rotation of upstream logs in the hopper by friction, and often causes a somewhat violent whipping motion of the logs entering the drum, which is restricted and contained by the upstream logs in the hopper and the thick walls of the hopper.
It has been proposed to feed tree length logs into a debarking drum with a nearly horizontal conveyor. To obtain efficient debarking, the tree length logs must be fed in groups of stacked or side by side logs. The problem with this technique is that the very long logs, perhaps sixty feet in length, begin to rotate and tumble soon after their leading ends enter the drum, while substantial lengths of the logs are still on the conveyor. The rotating and flailing motion of the logs can cause severe damage to the conveyor chain, and the trailing ends of logs leaving the conveyor can catch on and can be grabbed by the downwardly and rearwardly moving return portion of the conveyor. This can cause the trailing end of a log to be pushed down and pulled rearwardly so that the log jams in the chain while its leading end is whipped around by the drum. While the conveyor chain is quite strong and can support and move groups of heavy logs, localized stress in individual links caused by impact, or by grabbing a log at the nose end of the conveyor can damage the chain.
A further problem is that logs partly in the drum which are rotating tend to rotate trailing logs on the conveyor by friction.
There is therefor, a need for an efficient and reliable technique and apparatus for debarking logs of virtually any length, including tree length logs, in a rotating drum debarker.
SUMMARY OF THE INVENTION
In accordance with the invention a method and apparatus is provided for continuously debarking tree length logs in a rotary drum debarker, without danger of damage to the conveyor chain, and which is efficient, reliable, and quite economical.
This is accomplished by using a somewhat conventional chain conveyor, and providing an auxiliary feed means in the form of a conveyor or low friction feed region between the nose or head end of the chain conveyor and the debarking drum inlet, to avoid damage to the conveyor chain, while continuously feeding stacks or groups of any length logs, into the continuously rotating debarking drum.
The purpose of the auxiliary feed means or low friction region is to shield the head end of the main conveyor and to provide a region between the main conveyor and the drum inlet where there is minimal binding or jamming of trailing ends of logs being rotated by the drum.
In accordance with one aspect of the invention, the auxiliary feed means is a very rugged auxiliary conveyor located between the head end of the chain conveyor and the inlet of the debarking drum. In a preferred embodiment, this auxiliary conveyor is a feed roller driven independently of the conveyor chain, so that it can be driven at any desired surface speed i.e. the same as or faster or slower than the surface speed of the conveyor chain.
In accordance with another aspect of the invention, a short low friction region is provided between the conveyor and the inlet of the drum debarker. This region can be composed of one or more rotatable rollers.
In accordance with another aspect of the invention, a forward region of the main conveyor is provided with smooth upright sidewalls of a sufficient height to contain the trailing ends of the logs partly in the debarking drum, so the whipping motion of the logs is minimized. without hampering the forward movement of the logs into the debarking drum. A sidewall height higher than the elevation of the centerline of the debarking drum is usually necessary, but this height can be lower than the height of the top of the drum for construction economy.
A distinct advantage of the apparatus is that the conveyor has an open top along its entire length, so that the entire length of the conveyor is available for overhead loading of logs to be debarked. At the forward or head end of the conveyor, adjacent the debarking drum inlet, is a drum end protector plate, having an opening therein of a diameter slightly less than the inner diameter of the drum and which prevents the leading ends of the conveyed logs from impacting against the inlet end of the drum. Structural elements which extend over the head end of the conveyor are provided for securing the protector plate, but these elements are adjacent the inlet of the debarking drum and do not interfere with overhead loading of logs on the conveyor.
Accordingly, it is an object of the invention to provide a method and apparatus for continuously debarking tree length logs in a rotating drum debarker, by continuously feeding groups of tree length logs generally axially into the drum with a continuously driven main conveyor, and along a low friction region or auxiliary feed means between the discharge end of the main conveyor and the inlet of the drum.
Another object is a method and apparatus according to the above object in which the auxiliary feed means is an auxiliary conveyor.
Another object is a method and apparatus i
Price John P.
Woodham Donald V.
Bray W. Donald
Cox, Jr. Ray F.
Price Industries, Inc.
LandOfFree
Method and apparatus for debarking logs does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for debarking logs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for debarking logs will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2600950