CA1060316A - Barking drum - Google Patents
Barking drumInfo
- Publication number
- CA1060316A CA1060316A CA293,992A CA293992A CA1060316A CA 1060316 A CA1060316 A CA 1060316A CA 293992 A CA293992 A CA 293992A CA 1060316 A CA1060316 A CA 1060316A
- Authority
- CA
- Canada
- Prior art keywords
- drum
- barking
- log
- lifting elements
- lifting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27L—REMOVING BARK OR VESTIGES OF BRANCHES; SPLITTING WOOD; MANUFACTURE OF VENEER, WOODEN STICKS, WOOD SHAVINGS, WOOD FIBRES OR WOOD POWDER
- B27L1/00—Debarking or removing vestiges of branches from trees or logs; Machines therefor
- B27L1/04—Debarking or removing vestiges of branches from trees or logs; Machines therefor by rubbing the trunks in rotating drums
- B27L1/05—Drums therefor
Abstract
SPECIFICATION
ABSTRACT OF THE DISCLOSURE
A barking drum rotatable about a horizontal axis has a plurality of parallel ridge-like lifting elements on its inside wall. The lifting elements extend longitudinally of the drum and are inclined to its axis so that in moving upwardly as the drum rotates they raise the back ends of logs in the drum higher than the front ends without causing length-wise sliding of the logs. A sliding gate is disposed to be positioned transversely of the drum discharge outlet for controlling the log retention time in the drum.
ABSTRACT OF THE DISCLOSURE
A barking drum rotatable about a horizontal axis has a plurality of parallel ridge-like lifting elements on its inside wall. The lifting elements extend longitudinally of the drum and are inclined to its axis so that in moving upwardly as the drum rotates they raise the back ends of logs in the drum higher than the front ends without causing length-wise sliding of the logs. A sliding gate is disposed to be positioned transversely of the drum discharge outlet for controlling the log retention time in the drum.
Description
BACKGROUND OF THE INVENTION
The present invention relates to bar~ing drums for removing the bark from logs of wood. More particularly, it relates to a new and improved barking drum capable of barking whole trees by so-called parallel bar~ing.
1 6Z~
It has long been known to remove bark from logs by passing them through a rotating barking drum. Typical apparatus devised for this purpose, based on the so-called "tumbling barking" technique, is shown in U.S. patent No.
1,228,374 to Ross. There,barking is effected by introducing pieces of wood cut to relatively short lengths into a rotat-ing drum having a plurality of spaced devices spirally arranged on its inner surface for causing the wood to tumble over and over in complete disorder in passing from the inlet to the discharge end of the drum.
Apparatus based on a different technique known as "parallel barking" has also been proposed. In such apparatus, a more controlled orientation of the logs ta~es place in a direction towards the discharge end of the drum as they are fed forwardly and the logs roll and fall down instead of tumbling when they reach a certain level in the drum.
During barking the drum is partially filled with logs at the inlet end and the barking action is produced by subjecting the logs to impact and friction against each other during their passage through the drum as it rotates. Barkin~
irons on the inside wall of the drum have also been used to assist in lifting the logs during rotation and also for sub-jecting the logs to further frictional action. The barking action being dependent on the number of impacts and frictional impulses per unit of time, obviously it will increase with in-creased speed. If the speed is too high, however, the relative movement of the logs will diminish and eventually cease com-pletely. The barking action can also be increased by increasing '' ' ' ' the extent to which the drum is filled, i.e., by increasing the ratio of wood volume to drum volume. The increased barking action obtainable in this way, however, is limited by the rate of log flow desired or needed to maintain bal-anced barking.
The logs are fed forwardly through the drum in thefollowing way. As the drum rotates, the logs are lifted upwardly in the direction of rotation with their longi-tudinal axes substantially parallel to the axis of the drum and they then fall downwardly in the drum. Since it seldom happens, however, that a log is exactly parallel to the drum axis on falling, either the front or the back end of the log drops down first. In dropping, the free end of the log swings arollnd its upper end through an arc which intersects the drum 1~ at a location forwardly of the position it had before lt fell.
Tnus, a zig-zag movement of each log obtains as it moves through the drum and whether it moves towards the discharge end or the inlet end of the drum depends on which end of the log drops first. If the back end drops first, the log will feed for-wardly towards the discharge outlet of the drum, whereas ifthe frontend drops first, the log will feed rearwardly towards the inlet end.
To insure that the back ends of the logs will have more earlier falls than the front ends as required for forward movement through the drum, it has been the practice heretofore to fill the inlet end of the drum with enough logs to cause their back ends to be located further from the axis of rotation of the drum than their front ends. By so doing, the back ends 106()316 of the logs are subjected to less centrifugal force than the front ends and therefore tend to fall earlier.
It has also been proposed to provide barking drums that are tapered, inclined or of stepped shape to produce an increased difference in height of the logs between the inlet and discharge ends of the drum as required to obtain a zig-zag forward feed. Such expedients have not been satisfactory, however. In addition to high cost, they are all characterized by irregularities in the degree of filling of the drum and thus in the forward feed, as well as an uncontrollable re-tention time in the drum. For example, whereas the degree of filling at the inlet end of the drum can be 50 - 75%, at the discharge end it will be only 2 - 5%, a relatively poor utilization of capacity.
SUMMARY OF THE INVENTION
An object of the invention, accordingly, is to pro-vide a new and improved barking drum for removing bark from logs by "parallel barking" that is not subject to the above noted disadvantages of the prior art apparatus.
This and other objects of the invention are attained by providing a cylindrical barking drum rotatable about a substantially horizontal axis and having formed on the in-wide wall thereof a plurality of substantially parallel, ridge-like log lifting elements extending longitudinally of the drum for lifting the logs upwardly, as the drum rotates, to a level from which they fall downwards in the drum. The lifting elements are inclined with respect to the axis of rotatisn and the angle of inclination i5 suitably selected to lift the back ends of the raised logs higher than the front ends without permitting lengthwise sliding of the raised logs. Hence, the angle of inclination preferably should not exceed the angle of repose for a log on one of the lifting elements. In this manner, a zig-zag forward feed of the logs towards the discharge end of the drum is assured in a simple and effective manner with a suitably adapted retention time in the drum and with improved utilization of the drum capacity.
Where the log retention time in the drum must be controllable, controllable flow restricting means may be provided at the discharge end of the drum to regulate the size of the discharge opening. Such restricting means may suitably comprise a sliding gate disposed to be positioned transversely of the discharge opening.
DESCRIPTION OF A PREFERRED EMBODIMENT
For a better understanding of the invention, ref-erence is made to the following detailed description of a representative embodiment, taken in conjunction with the accompanying drawings, in which - Fig. 1 is a partial view in longitudinal section, taken along the line 1-1 of Fig. 2 and looking in the direc-tion of the arrows, of a barking drum constructed according to the invention;
- Fig. 2 is a side view of the discharge end of the barking drum shown in Fig. l;
- Fig. 3 is an end view of the barking drum as seen from the right in Fig. 2; and . . .
~, J ~ _~
~06~316 - Fig. 3a is a partial view in transverse section through one of the lifting elements in the barking drum.
As shown in Fig. 1, the barking drum of the inven-tion comprises a cylindrical drum lO mounted on conventional means (not shown) for rotation about a horizontal axis and having an inlet end 11 to which logs are adapted to be sup-plied for barking. On the inside wall of the drum lO are disposed a plurality of substantially parallel, ridge-like log lifting elements 12 which lift the logs upwardly as the drum rotates to a level from which they fall down into the drum. The lifting elements 12 may be generally arcuate in cross-section as shown in Figs. 3 and 3a and they extend in the longitudinal direction from the inlet end 11 to the outlet end 13 (Fig. 2) of the drum. Also, the lifting elements 12 are not parallel to the axis of rotation but have an angle of inclination with respect thereto such that the back ends of the logs, when raised to the level from which they are dropped, are higher than their front ends. The angle of inclination, however, should not exceed the angle of repose for a log on a lifting element 12, so as to avoid lengthwise sliding of the raised logs and uncontrolled transport of the logs through the drum.
Thus, for the direction of rotation indicated by the arrow A in Fig. 3, the lifting elements 12 in Fig. 1
The present invention relates to bar~ing drums for removing the bark from logs of wood. More particularly, it relates to a new and improved barking drum capable of barking whole trees by so-called parallel bar~ing.
1 6Z~
It has long been known to remove bark from logs by passing them through a rotating barking drum. Typical apparatus devised for this purpose, based on the so-called "tumbling barking" technique, is shown in U.S. patent No.
1,228,374 to Ross. There,barking is effected by introducing pieces of wood cut to relatively short lengths into a rotat-ing drum having a plurality of spaced devices spirally arranged on its inner surface for causing the wood to tumble over and over in complete disorder in passing from the inlet to the discharge end of the drum.
Apparatus based on a different technique known as "parallel barking" has also been proposed. In such apparatus, a more controlled orientation of the logs ta~es place in a direction towards the discharge end of the drum as they are fed forwardly and the logs roll and fall down instead of tumbling when they reach a certain level in the drum.
During barking the drum is partially filled with logs at the inlet end and the barking action is produced by subjecting the logs to impact and friction against each other during their passage through the drum as it rotates. Barkin~
irons on the inside wall of the drum have also been used to assist in lifting the logs during rotation and also for sub-jecting the logs to further frictional action. The barking action being dependent on the number of impacts and frictional impulses per unit of time, obviously it will increase with in-creased speed. If the speed is too high, however, the relative movement of the logs will diminish and eventually cease com-pletely. The barking action can also be increased by increasing '' ' ' ' the extent to which the drum is filled, i.e., by increasing the ratio of wood volume to drum volume. The increased barking action obtainable in this way, however, is limited by the rate of log flow desired or needed to maintain bal-anced barking.
The logs are fed forwardly through the drum in thefollowing way. As the drum rotates, the logs are lifted upwardly in the direction of rotation with their longi-tudinal axes substantially parallel to the axis of the drum and they then fall downwardly in the drum. Since it seldom happens, however, that a log is exactly parallel to the drum axis on falling, either the front or the back end of the log drops down first. In dropping, the free end of the log swings arollnd its upper end through an arc which intersects the drum 1~ at a location forwardly of the position it had before lt fell.
Tnus, a zig-zag movement of each log obtains as it moves through the drum and whether it moves towards the discharge end or the inlet end of the drum depends on which end of the log drops first. If the back end drops first, the log will feed for-wardly towards the discharge outlet of the drum, whereas ifthe frontend drops first, the log will feed rearwardly towards the inlet end.
To insure that the back ends of the logs will have more earlier falls than the front ends as required for forward movement through the drum, it has been the practice heretofore to fill the inlet end of the drum with enough logs to cause their back ends to be located further from the axis of rotation of the drum than their front ends. By so doing, the back ends 106()316 of the logs are subjected to less centrifugal force than the front ends and therefore tend to fall earlier.
It has also been proposed to provide barking drums that are tapered, inclined or of stepped shape to produce an increased difference in height of the logs between the inlet and discharge ends of the drum as required to obtain a zig-zag forward feed. Such expedients have not been satisfactory, however. In addition to high cost, they are all characterized by irregularities in the degree of filling of the drum and thus in the forward feed, as well as an uncontrollable re-tention time in the drum. For example, whereas the degree of filling at the inlet end of the drum can be 50 - 75%, at the discharge end it will be only 2 - 5%, a relatively poor utilization of capacity.
SUMMARY OF THE INVENTION
An object of the invention, accordingly, is to pro-vide a new and improved barking drum for removing bark from logs by "parallel barking" that is not subject to the above noted disadvantages of the prior art apparatus.
This and other objects of the invention are attained by providing a cylindrical barking drum rotatable about a substantially horizontal axis and having formed on the in-wide wall thereof a plurality of substantially parallel, ridge-like log lifting elements extending longitudinally of the drum for lifting the logs upwardly, as the drum rotates, to a level from which they fall downwards in the drum. The lifting elements are inclined with respect to the axis of rotatisn and the angle of inclination i5 suitably selected to lift the back ends of the raised logs higher than the front ends without permitting lengthwise sliding of the raised logs. Hence, the angle of inclination preferably should not exceed the angle of repose for a log on one of the lifting elements. In this manner, a zig-zag forward feed of the logs towards the discharge end of the drum is assured in a simple and effective manner with a suitably adapted retention time in the drum and with improved utilization of the drum capacity.
Where the log retention time in the drum must be controllable, controllable flow restricting means may be provided at the discharge end of the drum to regulate the size of the discharge opening. Such restricting means may suitably comprise a sliding gate disposed to be positioned transversely of the discharge opening.
DESCRIPTION OF A PREFERRED EMBODIMENT
For a better understanding of the invention, ref-erence is made to the following detailed description of a representative embodiment, taken in conjunction with the accompanying drawings, in which - Fig. 1 is a partial view in longitudinal section, taken along the line 1-1 of Fig. 2 and looking in the direc-tion of the arrows, of a barking drum constructed according to the invention;
- Fig. 2 is a side view of the discharge end of the barking drum shown in Fig. l;
- Fig. 3 is an end view of the barking drum as seen from the right in Fig. 2; and . . .
~, J ~ _~
~06~316 - Fig. 3a is a partial view in transverse section through one of the lifting elements in the barking drum.
As shown in Fig. 1, the barking drum of the inven-tion comprises a cylindrical drum lO mounted on conventional means (not shown) for rotation about a horizontal axis and having an inlet end 11 to which logs are adapted to be sup-plied for barking. On the inside wall of the drum lO are disposed a plurality of substantially parallel, ridge-like log lifting elements 12 which lift the logs upwardly as the drum rotates to a level from which they fall down into the drum. The lifting elements 12 may be generally arcuate in cross-section as shown in Figs. 3 and 3a and they extend in the longitudinal direction from the inlet end 11 to the outlet end 13 (Fig. 2) of the drum. Also, the lifting elements 12 are not parallel to the axis of rotation but have an angle of inclination with respect thereto such that the back ends of the logs, when raised to the level from which they are dropped, are higher than their front ends. The angle of inclination, however, should not exceed the angle of repose for a log on a lifting element 12, so as to avoid lengthwise sliding of the raised logs and uncontrolled transport of the logs through the drum.
Thus, for the direction of rotation indicated by the arrow A in Fig. 3, the lifting elements 12 in Fig. 1
2~ are moving upwardly and a log 14 is shown being lifted by one of them. It will be noted that the lifting elements 12 on the lifting side of the drum lO slope downwardly from the inlet end to the discharge end and that the inlet or back end ~ ' ' -of the log 14 is higher than the front or outlet end. The angle of inclination ~ of the lifting elements 12, however, should preferably not exceed the angle of repose of the log 14 on the lifting element 12, so that the raised logs do not slide lengthwise of the drum. Stated mathematically, arc tan ~ > ~
where ~ is the coefficient of friction between a log and a lifting element 12.
As best shown in Fig. 3a, the lifting elements 12 should preferably be arc or hyperbola shaped in cross-section, with substantially straight sides 15 and 16 and rounded tops 17. Desirabl~, the angle y between each of the sides 15 and 16 and a tangent to the inner surface of the drum 10 should be between 30 and 60. Also, the thickness of the material from which the lifting elements 12 are made may- advantageously be a maximum at the top 17 and decrease to a minimum towards the sides 15 and 16. For example, lifting elements 12 having a top thickness tl of 25 mm. reducing to a side thickness t2 of 15 mm. at the drum 10 can have one-third longer life than lifting elements 12 of uniform 20 mm. thickness.
For optimal operation, the radial height h of the lifting elements 12 above the inner surface of the drum 10 should be about 0.75 to 1.25 of half the average log diameter;
the angle B between adjacent lifting elements 12 should be about 30 maximum; and the axial length of the barking drum 10 should be at least twice the drum diameter. For angles much greater than 30 the frequency of lifting of the logs ~ _ . ......
and therefore the capacity is decreased. While the angle ~ may be less than 30, if it is made too small, it has the effect of increasing the number of lifting elements without accompanying additional advantages.
At the discharge end 13 of the drum is disposed means for regulating the size of the discharge opening as required to control the log retention time in the drum.
Such means may comprise a plate 18 mounted in conventional retainer means (not shown) for sliding movement across the drum discharge opening in opposite directions as indicated by the arrow B and haYing an inclined forward edge 19. It will be understood that as the plate 1~ is moved from the full line position to the dot-dash position in Fig. 3, the size of the drum discharge opening is gradually reduced.
The invention thus provides a simple and economi-cally advantageous barking drum for removing bark from logs.
By utilizing angularly inclined log lifting means inside the drum as described above, the back ends of the logs are lifted higher than the front ends so that the back ends drop first when they fall into the drum. Accordingly, a zig-zag log movement is produced which advances the logs effectively towards the discharge end of the drum. In addition, the controllable discharge opening restricting means enables the log retention time in the drum and thereby the barking process to be controlled as required to accommodate different grades of wood.
The specific emhodiment described is only illus-trative and is susceptible of modiication in form and detail ~7ithin the scope of the following claims.
,, , , ~, . . . .. .... . . . . . . . .
where ~ is the coefficient of friction between a log and a lifting element 12.
As best shown in Fig. 3a, the lifting elements 12 should preferably be arc or hyperbola shaped in cross-section, with substantially straight sides 15 and 16 and rounded tops 17. Desirabl~, the angle y between each of the sides 15 and 16 and a tangent to the inner surface of the drum 10 should be between 30 and 60. Also, the thickness of the material from which the lifting elements 12 are made may- advantageously be a maximum at the top 17 and decrease to a minimum towards the sides 15 and 16. For example, lifting elements 12 having a top thickness tl of 25 mm. reducing to a side thickness t2 of 15 mm. at the drum 10 can have one-third longer life than lifting elements 12 of uniform 20 mm. thickness.
For optimal operation, the radial height h of the lifting elements 12 above the inner surface of the drum 10 should be about 0.75 to 1.25 of half the average log diameter;
the angle B between adjacent lifting elements 12 should be about 30 maximum; and the axial length of the barking drum 10 should be at least twice the drum diameter. For angles much greater than 30 the frequency of lifting of the logs ~ _ . ......
and therefore the capacity is decreased. While the angle ~ may be less than 30, if it is made too small, it has the effect of increasing the number of lifting elements without accompanying additional advantages.
At the discharge end 13 of the drum is disposed means for regulating the size of the discharge opening as required to control the log retention time in the drum.
Such means may comprise a plate 18 mounted in conventional retainer means (not shown) for sliding movement across the drum discharge opening in opposite directions as indicated by the arrow B and haYing an inclined forward edge 19. It will be understood that as the plate 1~ is moved from the full line position to the dot-dash position in Fig. 3, the size of the drum discharge opening is gradually reduced.
The invention thus provides a simple and economi-cally advantageous barking drum for removing bark from logs.
By utilizing angularly inclined log lifting means inside the drum as described above, the back ends of the logs are lifted higher than the front ends so that the back ends drop first when they fall into the drum. Accordingly, a zig-zag log movement is produced which advances the logs effectively towards the discharge end of the drum. In addition, the controllable discharge opening restricting means enables the log retention time in the drum and thereby the barking process to be controlled as required to accommodate different grades of wood.
The specific emhodiment described is only illus-trative and is susceptible of modiication in form and detail ~7ithin the scope of the following claims.
,, , , ~, . . . .. .... . . . . . . . .
Claims (11)
1. A cylindrical barking drum mounted for rotation about a generally horizontal axis and having an inlet, an outlet and a plurality of substantially parallel inwardly directed log lifting elements mounted on the inside wall of the drum and extending longituni-nally thereof for lifting logs upwardly in the drums it rotates,to a level from which they fall into the drum, in which the log lifting elements have angles of inclina-tion in relation to the rotational axis of the drum such that the logs, when lifted by the lifting elements to the level from which they fall, have their back ends higher than their front ends, yet do not slide lengthwise towards the drum outlet.
2. A barking drum as defined in claim 1 in which the angular inclination of the lifting elements with respect to the axis of rotation is such that,in moving upwardly as the drum rotates,the lifting elements incline downwardly from the inlet end to the outlet end of the drum, but is less than the coefficient of friction between a log and a lifting element.
3. A barking drum as defined in claim 2 in which the log lifting elements are smoothly curved transversely of their longitudinal axes.
4. A barking drum as defined in claim 3 in which the log lifting elements are generally arcuate in cross-section with rounded tops and substantially straight sides intersecting the inner surface of the drum at an acute angle.
5. A barking drum as defined in claim 4 in which the angle between each straight lifting element side and the tangent to the inner surface of the drum at the place of intersection is between 30° and 60°.
6. A barking drum as defined in claim 5 in which the radial height of the top of each lifting element from the inner surface of the drum is about 0.75 to 1.25 of one-half the average log diameter.
7. A barking drum as defined in claim 6 in which the lifting element thickness is a maximum at the top and is less at the sides thereof.
8. A barking drum as defined in claim 7 in which the angular spacing between adjacent pairs of lifting elements about the axis of rotation of the drum does not exceed about 30°.
9. A barking drum as defined in claim 8 in which the drum length is at least twice the drum diameter.
10. A barking drum as defined in claim 1 together with controllable restriction means disposed at the outlet end of the drum for regulating the size of the discharge opening in the drum and thereby the log retention time in the drum.
11. A barking drum as defined in claim 10 in which the restriction means comprises a gate slidably mounted for movement transversely of the discharge opening and in proximity thereto.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7614643A SE7614643L (en) | 1976-12-28 | 1976-12-28 | BARKTRUMMA |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1060316A true CA1060316A (en) | 1979-08-14 |
Family
ID=20329866
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA293,992A Expired CA1060316A (en) | 1976-12-28 | 1977-12-28 | Barking drum |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1060316A (en) |
| SE (1) | SE7614643L (en) |
-
1976
- 1976-12-28 SE SE7614643A patent/SE7614643L/en unknown
-
1977
- 1977-12-28 CA CA293,992A patent/CA1060316A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| SE7614643L (en) | 1978-06-29 |
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