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Title:
DEBARKING OF LOGS
Document Type and Number:
WIPO Patent Application WO/2005/023498
Kind Code:
A1
Abstract:
A debarker roller (10) has an axis of rotation (16) and includes at least one bark cutting edge (20) arranged to rotate in a zone transverse to the axis of rotation (16). The cutting edge (20) has at least one direction change where the direction of the cutting edge (20) changes relative to the direction of the axis of rotation (16).

Inventors:
KUESEL ECKART FRIEDRICH (ZA)
Application Number:
PCT/IB2004/050441
Publication Date:
March 17, 2005
Filing Date:
April 15, 2004
Export Citation:
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Assignee:
KUESEL ECKART FRIEDRICH (ZA)
International Classes:
B27L1/10; (IPC1-7): B27L1/10
Foreign References:
DE742608C1943-12-08
DE529087C1931-07-08
Attorney, Agent or Firm:
Van Der, Walt Louis Stephanus (Adams & Adams Place 1140 Prospect Stree, Hatfield P O Box 1014 0001 Pretoria, ZA)
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Claims:
Claims
1. A debarker roller which has an axis of rotation and which includes at least one bark cutting edge arranged to rotate in a zone transverse to the axis of rotation, the cutting edge having at least one direction change where the direction of the cutting edge changes relative to the direction of the axis of rotation.
2. The debarker roller as claimed in claim 1, in which the cutting edge is a continuous endless edge extending circumferentially about the axis of rotation.
3. The debarker roller as claimed in claim 1 or claim 2, which includes a roller body, the cutting edge being defined by a bark cutting formation mounted or secured to the roller body to stand proud of the roller body.
4. The debarker roller as claimed in claim 3, which includes a plurality of axially spaced bark cutting formations defining bark cutting edges, with the edges being arranged to rotate in axially spaced or adjacent zones transverse to the axis of rotation, the bark cutting formations being in the form of blades defining the bark cutting edges, and the blades being mounted on the roller body so that the bark cutting edges are remote from the roller body.
5. The debarker roller as claimed in claim 4, in which adjacent axially spaced blades define between them a circumferentially extending gap or space which frequently changes width along its path.
6. The debarker roller as claimed in claim 5, in which two adjacent axially spaced bark cutting edges are spaced in an axial direction between about 8 mm and about 20 mm where they are closest to each other.
7. The debarker roller as claimed in any one of the preceding claims, in which the bark cutting edge, or at least a portion thereof, is sinuous or wavy.
8. The debarker roller as claimed in claim 6, in which adjacent axially spaced endless sinuous bark cutting edges are arranged out of phase, defining between them a circumferentially extending gap or space which repetitively narrows and widens endlessly.
9. The debarker roller as claimed in any one of claims 1 to 5 inclusive, in which at least a portion of the bark cutting edge has a zigzag configuration when the roller is viewed in plan.
10. The debarker roller as claimed in any one of claims 7 to 9 inclusive, in which the bark cutting edge, when sinusoidal or of zigzag configuration, as the case may be, has a unit length of between about 60 mm and about 100 mm, where the unit length is a concept equivalent or similar to the concept of a wavelength of a sine wave.
11. A debarker which includes at least one driven debarker roller as claimed in any one of claims 1 to 10 inclusive.
12. The debarker as claimed in claim 11, which includes at least one further driven roller or feed roller, the debarker roller and the further driven roller being arranged to receive a log between them so that ends of the log will protrude sideways from between the rollers, i. e. the received log extending transversely to the axes of rotation of the rollers.
13. The debarker as claimed in claim 12, in which the further driven roller includes log engaging formations.
14. The debarker as claimed in claim 13, in which the log engaging formations are in the form of elongate axially extending, circumferentially spaced blades or formations.
15. A method of debarking a log, which includes axially displacing the log in contact with and between at least two spaced rollers of which at least one is a debarker roller, the log extending transversely to axes of rotation of the rollers and the debarker roller having at least one bark cutting edge arranged to rotate in a zone parallel to a longitudinal axis of the log, the cutting edge having at least one direction change where the direction of the cutting edge changes relative to the longitudinal axis of the log.
16. The method as claimed in claim 15, in which the debarker roller is a roller as claimed in any one of claims 1 to 10 inclusive.
17. The method as claimed in claim 15 or claim 16, in which the log is axially displaced at a linear speed of between about 3.5 m/s and about 5.5 m/s.
18. The method as claimed in any one of claims 15 to 17 inclusive, in which the log is axially displaced at least twice and in opposite axial directions, and in which the log is rotated about its longitudinal axis at least once.
19. The method as claimed in any one of claims 15 to 18 inclusive, in which the log is a log of a gum tree specie.
Description:
Description DEBARKING OF LOGS [1] THIS INVENTION relates to debarking of logs. In particular, it relates to a debarker roller, to a debarker and to a method of debarking a log.

[2] The Applicant is aware of debarkers which are well suited for use on pine tree logs.

However, these debarkers do not perform well with logs of the gum tree species such as the Eucalyptus tree. These conventional debarkers also perform particularly poorly in drier seasons.

[3] According to one aspect of the invention, there is provided a debarker roller which has an axis of rotation and which includes at least one bark cutting edge arranged to rotate in a zone transverse to the axis of rotation, the cutting edge having at least one direction change where the direction of the cutting edge changes relative to the direction of the axis of rotation.

[4] Preferably, the cutting edge is a continuous endless edge extending circum- ferentially about the axis of rotation. However, a broken cutting edge comprising a plurality of edge portions arranged circumferentially about the axis of rotation, whether touching or spaced from one another, is not excluded from the scope of the invention.

Typically, the cutting edge has a plurality of direction changes, e. g. 15 to 60, preferably 20 to 40 direction changes.

[5] The debarker roller may include a roller body. The cutting edge may be defined by a bark cutting formation mounted or secured to the roller body to stand proud of the roller body.

[6] Typically, the debarker roller includes a plurality (e. g. 3 to 8) of axially spaced bark cutting formations defining bark cutting edges, with the edges being arranged to rotate in axially spaced or adjacent zones transverse to the axis of rotation. The bark cutting formations may be in the form of blades defining the bark cutting edges, the blades being mounted on the roller body so that the bark cutting edges are remote from the roller body.

[7] Adjacent axially spaced blades may define between them a circumferentially extending gap or space which frequently changes width along its path.

[8] Two adjacent axially spaced bark cutting edges may be spaced in an axial direction between about 8 mm and about 20 mm where they are closest to each other.

Preferably, two adjacent axially spaced bark cutting edges are spaced in an axial direction between about 10 mm and about 16 mm, e. g. about 12 mm, where they are closest to each other.

[9] The bark cutting edge, or at least a portion thereof, may be sinuous or wavy. At least a portion of the bark cutting edge may thus be sinusoidal when the roller is viewed in plan. Instead, at least a portion of the bark cutting edge may have a zigzag configuration when the roller is viewed in plan. Typically, when the roller is seen in end view, the bark cutting edge is circular, or at least falls on the outline of a circle.

[10] In one embodiment of the invention, adjacent axially spaced endless sinuous bark cutting edges are arranged out of phase, defining between them a circumferentially extending gap or space which repetitively narrows and widens endlessly.

[11] The bark cutting edge, when sinusoidal or of zigzag configuration, as the case may be, may have a unit length of between about 60 mm and about 100 mm, where the unit length is a concept equivalent or similar to the concept of a wavelength of a sine wave.

Preferably, the unit length is between about 70 mm and about 90 mm, e. g. about 81 mm.

[12] According to another aspect of the invention, there is provided a debarker which includes at least one driven debarker roller as hereinbefore described.

[13] Typically, the debarker includes at least one further driven roller or feed roller, the debarker roller and the further driven roller being arranged to receive a log between them so that ends of the log will protrude sideways from between the rollers, i. e. the received log extending transversely to the axes of rotation of the rollers.

[14] The further driven roller may include log engaging formations. In one embodiment of the invention, the log engaging formations are in the form of elongate axially extending, circumferentially spaced blades or formations.

[15] The rollers typically have substantially the same maximum diameter. The maximum diameter and the angular speed of rotation of the rollers in use are typically selected such that a log caught between the rollers is displaced axially at a linear speed of between about 3.5 m/s and about 5.5 m/s, e. g. about 4 m/s, whilst being debarked.

[16] The maximum diameter of the roller is preferably between about 35 cm and about 50 cm, more preferably between about 40 cm and about 45 cm, e. g. about 42 cm.

[17] The debarker may include drive means configured to rotate the rollers at an angular speed of rotation of between about 160 rpm and about 200 rpm, preferably between about 170 rpm and about 190rpm, e. g. about 182 rpm. In one embodiment of the invention, the drive means is a hydraulic drive means.

[18] Typically, the debarker includes at least two spaced log grabbing devices to grab a log at two axially spaced locations, with the rollers typically being located between these two locations, i. e. between the log grabbing devices. These log grabbing devices may be of conventional form, e. g. each comprising a pair of grab jaws which have curved inner surfaces so that the jaws, when closed, surround a log with sufficient contact between the log and the jaws being established safely to manipulate the log by means of the jaws.

[19] Typically, the axis of rotation of the debarker roller and the further driven roller are parallel and upwardly extending, e. g. vertical.

[20] The debarker may include a cleaning formation to clean the debarking roller.

[21] According to a further aspect of the invention, there is provided a method of debarking a log, which includes axially displacing the log in contact with and between at least two spaced rollers of which at least one is a debarker roller, the log extending transversely to axes of rotation of the rollers and the debarker roller having at least one bark cutting edge arranged to rotate in a zone parallel to a longitudinal axis of the log, the cutting edge having at least one direction change where the direction of the cutting edge changes relative to the longitudinal axis of the log.

[22] The debarker roller may be a debarker roller as hereinbefore described.

[23] The log may be axially displaced at a linear speed of between about 3.5 m/s and about 5.5 m/s, e. g. about 4 m/s.

[24] The log may be axially displaced at least twice and in opposite axial directions, and may be rotated about its longitudinal axis at least once.

[25] The log may be a log of a gum tree specie.

[26] The invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which [27] Figure 1 shows, in combination, a top plan view of a debarker roller in accordance with the invention and a cleaning formation of a debarker; and [28] Figure 2 shows a bottom plan view of a debarker in accordance with the invention.

[29] Referring to Figure 1 of the drawings, reference numeral 10 generally indicates a debarker roller in accordance with the invention and reference numeral 12 generally indicates a cleaning formation in use to clean the debarker roller 10.

[30] The roller 10 comprises a steel roller body 14 which is circular cylindrical and which defines an axis of rotation 16 for the roller 10. The roller 10 further comprises five axially spaced bark cutting formations, in the form of steel blades 18, each of which defines a bark cutting edge 20 which is thus arranged to rotate in a zone transverse to the axis of rotation 16, when the roller 10 is rotated. Each blade 18 has a height of about 35 mm and is thus mounted to be radially extending from the roller body 14.

[31] In accordance with the invention, and as can be clearly seen in Figure 1 of the drawings, each cutting edge 20 is sinusoidal, thus having a plurality of direction changes relative to the direction of the axis of rotation 16.

[32] In the embodiment of the invention shown in the drawings, each cutting edge 20 is a continuous, endless edge which extends circumferentially about the axis of rotation 16. Adjacent cutting edges 20 are spaced, in an axial direction, about 12 mm where they are closest to each other. In other words, the minimum distance between adjacent cutting edges 20 of the roller 10 shown in the drawings is about 12 mm. A space 21 between adjacent blades 18 thus frequently changes width if the space 21 is followed along its circular path.

[33] Each cutting edge 20 has a unit length of about 82mm, where the unit length is the distance between adjacent crests or between adjacent troughs of the sinusoidal figure described by the cutting edge 20.

[34] Referring to Figure 2 of the drawings, reference numeral 30 generally indicates a debarker in accordance with the invention. The debarker 30 includes the debarker roller 10 of the invention and a feed roller 32 arranged to rotate about an axis of rotation 34. As can be clearly seen in Figure 2, the axes of rotation 16,34 are parallel and in use vertical. A log receiving gap 34 is defined between the spaced rollers 10,32.

[35] The rollers 10,32 are mounted such that the distance between the axes 16,34 can be increased to receive a log, and then decreased again in order to allow the rollers 10, 32 to engage the log. In other words, the gap 34 between the rollers 10,32 is variable.

The mechanism for opening and closing the gap 34 between the rollers 10,32, is con- ventional and is not explained herein.

[36] As shown in Figure 2 of the drawings, the rollers 10,32 are arranged to receive a log 36, shown in broken lines in Figure 2, between the rollers 10,32. The log 36 thus extends transversely to the axes of rotation 16,34 of the rollers 10,32 respectively.

[37] The roller 32 includes a plurality of log engaging formations in the form of axially extending, circumferentially spaced steel blades 38.

[38] The maximum diameter of the roller 10 and the maximum diameter of the roller 32 are substantially the same so that, when the rollers 10,32 are rotated in opposite directions, the log 36 is displaced axially, preferably with no slippage taking place between any of the rollers 10,32 and the log 36. Typically, the rollers 10,32 are di- mensioned and rotated such that the linear axial speed of the log 36 being displaced between the rollers 10,32 is about 4 m/s, whilst the log 36 is being debarked.

[39] The debarker 30 includes hydraulic drive means (not shown) to drive the rollers 10, 32 and also includes the cleaning formation 12, which can be seen in more detail in Figure 1 of the drawings. The cleaning formation 12 includes four scraper fingers 40 which are arranged in the gaps or spaces 21 between adjacent blades 18 in use to clean the debarker roller 10 of bark.

[40] The debarker 30 includes two log grabbing devices 50,60 on diagonally opposite sides of the rollers 10,32. The log grabbing devices 50,60 are of conventional con- struction and respectively include a pair of grab jaws 52 and a pair of grab jaws 62.

The jaws 52,62 are pivotally displaceable about pivot shafts 54,64. The jaws 52,62 have curved inner surfaces and are roughly sickle-shaped allowing the jaws 52,62, when closed, to surround a log with sufficient contact between the log and the jaws 52, 62 being established safely to manipulate the log by means of the jaws 52,62.

[41] The log grabbing devices 50,60 are displaceable so they can be lowered to grab a log and then lifted to locate the log between the rollers 10,32. The mechanisms providing the mobility to the log grabbing devices 50,60 are conventional and known to those skilled in the art, and will not be described herein.

[42] In use, the debarker 30 is located over a log, typically a log lying on the ground, with the rollers 10,32 depending downwardly. The rollers 10,32 are displaced away from each other, if necessary, so that the gap 34 is large enough to receive the log and the log grabbing devices 50,60 are lowered and the jaws 52,62 operated to grab the log at axially spaced locations. The log grabbing devices 50,60 are then lifted to pull the log into the gap 34 so that the log is arranged relative to the rollers 10,32 in the fashion as illustrated by the log 36 in Figure 1 of the drawings. The gap 34 between the rollers 10,32 is then reduced so that the log is squeezed between the rollers 10,32.

With the rollers 10,32 then being rotated in opposite directions, with the directions being changed as desired, the log 36 is axially displaced forwards and backwards between the rollers 10,32, in order to debark the log. During the axial displacement of the log 36, the cutting edges 20 of the roller 10 cut the bark whilst the roller 32 ensures that the log 36 is driven backwards and forwards. With the linear speed of the log 36 being about 4 m/s, it is typically necessary to pass the log between one and three times between the rollers 10,32, in order to debark the log. As will be appreciated, in order to allow the log 36 to be displaced axially, the jaws 52,62 must not grab the log 36 too tightly, so that the log 36 can slide between the jaws 52 and the jaws 62. It will also be appreciated that the jaws 52,62, as a result of the friction between the log 36 and the jaws 52,62, assist in the debarking of the log 36.

[43] If it is necessary to rotate the log 36 about its longitudinal axis, this can be ac- complished by opening one of the pairs of jaws 52,62 to some extent to allow that end of the log 36 to drop below the other end of the log 36. As a result of the relative orientation of the rotating blades 38 and the log 36, rotational forces are then acting on the log 36, causing the log 36 to rotate about its longitudinal axis.

[44] The Applicant has surprisingly found that the debarker roller of the invention, as il- lustrated, when forming part of a debarker as illustrated, provides for up to about 40 % improvement in production compared to conventional debarkers. The debarker of the invention, as illustrated, is also capable of easily debarking logs of gum tree species such as the Eucalyptus tree, and can handle logs with lengths up to about 25 metres.




 
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