EP3259103B1

EP3259103B1 - Method and device for producing wood lamellae

Info

Publication number: EP3259103B1
Application number: EP16751994.1A
Authority: EP
Inventors: Markus HIRMKE; Andreas Rainer
Original assignee: Stora Enso Oyj
Current assignee: Stora Enso Oyj
Priority date: 2015-02-17
Filing date: 2016-02-08
Publication date: 2021-12-15
Anticipated expiration: 2036-02-08
Also published as: PL3259103T3; SE1550171A1; EP3259103A4; SE538849C2; WO2016132246A1; EP3259103A1

Description

Technical Field

The present disclosure relates to a method and a device for cutting a log into pieces which may be joined to form a structural member, which may be used as a beam, a joist, a stud, a pillar, a panel, a board, a wall element or the like.

Background

Currently, glue-laminated beams ("gluelam") in Europe are mostly produced according to DIN 1052:2008 (German standard) or DIN EN 14080: 2013-09 (harmonized European standard). The beams are built up with visually graded or machine graded boards, which are produced and kiln-dried in sawmills in the traditional way.
The gluelam producer takes these boards as raw material, grades them and produces the required lamellae by cutting out defects (e.g. knots) and finger-jointing the pieces together. After the finger-jointed lamellae have been planed, glue is applied and the beam is formed by gluing the lamellae together. The final steps may comprise planing the beam, removing optical defects, packaging and loading it.
Hence, traditionally, timber is sawn into planks or lamellae according to the scheme depicted in Fig. 1 of US5816015 , which discloses alternative methods of forming wood beams by laminating together a plurality of planks or lamellae.
EP1277552A2 discloses a similar method of forming a wood beam by cutting a round piece of timber into a plurality of strips having a trapezoidal cross section and laminating together the pieces thus formed into a beam.
US4122878 discloses a method of converting balsa wood of relatively small diameter into panels. US2005034786 discloses a radial sawing method for sawing raw logs.
The present applicant has realized that there is a potential for obtaining an even stronger structural member, which may be constructed generally as is illustrated in Fig. 1a-1c. Such a structural member may comprise a plurality of glued-together wood lamellae, each having a lamella cross section which is parallel with a cross section of the structural member and a longitudinal direction which is parallel with a longitudinal direction of the structural member and with a principal grain direction of the wood lamellae. Such lamellae may be formed as radial sections of a log and present cross sections which are triangular or trapezoidal and present a respective base surface that is formed at a radially outer part of the log. The lamellae are arranged as at least one layer in which base surfaces of a pair of immediately adjacent lamellae face opposite directions.
Fig. 1a schematically illustrates the simplest form of beam or joist that can be formed with a single layer of lamellae 20a, 20b which are laminated side by side with major base surfaces facing alternating upwardly and downwardly, respectively.
Fig. 1b schematically illustrates a two-layer beam or joist. This beam is thus formed by two layers L1, L2 of lamellae, each of which is formed in the same manner as the single layer of Fig. 1a. The layers L1, L2 may be laminated together by gluing using conventional gluing technique. In order to provide a longer structural member, it is possible to join together layers L1, L2 of lamellae, e.g. by finger jointing, prior to the joining of the layers. L1, L2 to form the structural member.
Fig. 1c schematically illustrates a three-layer beam or joist that is similar to that of Fig. 1b. Hence, in this embodiment, the beam is formed of three layers L1, L2, L3 of lamellae 20a, 20b.
Each layer may typically have a thickness of about 5-20 cm, preferably about 10-15 cm. A beam may be formed of as many layers as deemed necessary. Current standard beams are available at a height of up to 1.2 m, which would translate into a beam having 6-24 layers. Most likely, a beam of that height would have 10-12 layers.
In view of this new type of beam, there is a need for a more efficient device and method of producing lamellae having a trapezoidal cross section.

Summary

It is a general object of the present invention to provide a method and device for producing wood pieces having trapezoidal cross section that may be used for producing an improved structural member, such as a beam, a joist, a stud, a pillar, a panel, a board, a wall element, or the like. Preferably, such method and device should be suited for large scale production. Moreover, such method and device should be suited to provide products with very narrow tolerances.
The invention is defined by the appended independent claims. Embodiments are set forth in the dependent claims, in the following description and in the attached drawings.
According to a first aspect, there is provided a method of producing a plurality of wood lamellae having an approximately trapezoidal cross section. The method comprises providing a half log having a semicircular cross section, presenting a convex surface and a planar surface, cutting a groove at a central portion of the planar surface, such that the groove extends along a length direction of the log, cutting at least two radial cuts, each extending from the convex surface to the groove, such that at least three wood lamellae are formed.
By cutting the groove, the segments may be readily separated from each other, while the radial cutters may be sufficiently spaced from each other to avoid collision. The number of cutters may be between two and fifteen preferably five or seven.
The method may further comprise scanning the log to determine at least one dimension of the log. The scanning may take place before cutting the radial cuts and either before or after cutting the groove.
For example, the entire half log may be scanned whereby an approximation of the log in the form of a half cylinder or a half truncated cone may be provided.
The method may further comprise using the dimension for determining at least one of an intended position and extent of the groove, and intended positions and extents of the radial cuts.
Hence the cutting of the log may be optimized based on the measurement.
In the method the at least two radial cuts may be separated by an angle of 60°, 45°, 36°, 30°, 22.5°, 18°, 15°, 12.9° or 11.25° about a central axis C of the log.
The at least two radial cuts are provided substantially simultaneously.
Hence, the cutting may be performed by cutters which are spaced from each other in the longitudinal direction of the log, or which are at the same longitudinal position.
The radial cuts may extend past a surface of the groove by less than % of a groove depth, preferably less than ½ or less than ¼ of the groove depth.
A "groove surface" is a surface that is formed in the groove in connection with the cutting. This groove surface may have a generally concave cross section, which may be semicircular or polygonal.
The method may further comprise face cutting the convex surface, such that a first base surface is provided, extending between intersections of the radial cuts and the convex surface.
The method may further comprise following a line along the length direction that is derived based on an outer surface of the log when face cutting the convex surface.
By following a line derived based on the outer surface of the log, it is possible to retain as many of the outside fibers as possible, which is advantageous, since these are the wood fibres which have the best strength properties when they are used in load bearing wood products. Hence, it is preferred to follow the outer surface rather than the pith.
The face cutting of the convex surface may be performed before cutting the radial cuts.
The method may further comprise face cutting the groove surface, such that a second base surface is provided, which is parallel to the first base surface.
The method may further comprise following the first base surface when face cutting the groove surface.
The second base surface may be parallel to the first base surface. When cutting the second base surface, the first base surface may used as a guide surface.
The face cutting of the groove surface may be performed after cutting the radial cuts.
According to a second aspect, there is provided a device for producing a plurality of wood lamellae having an approximately trapezoidal cross section. The device comprises a feed device for providing a log having a semicircular cross section, presenting a convex surface and a planar surface, a groove cutter, arranged to cut a groove at a central portion of the planar surface, such that the groove extends along a length direction of the log, at least two radial cutters, each arranged to provide a cut extending from the convex surface to the groove and longitudinally along the log, such that at least three wood lamellae are formed.
The device may further comprise means for scanning the log to derive at least one dimension of the log.
The device may further comprise a first face cutter, arranged to cut into the convex surface so as to provide a first base surface.
The base surface may extend substantially along the length direction of the log.
The first face cutter may be moveable in a radial direction of the log, such that the cutting of the first base surface may follow a line along the length direction that is derived based on an outer surface of the log.
The device may further comprise a second face cutter, arranged to cut into the groove surface so as to provide a second base surface.
This second base surface may also extend substantially along the length direction of the log.
Preferably, the second face cutter is arranged to provide a constant distance between the first base surface and the second base surface.

Brief Description of the Drawings

Figs 1a-1c are schematic sectional views of a beam or joist produced from wood lamellae having a trapezoidal cross section.
Fig. 2 is a schematic view of a cutting arrangement according to a first embodiment.
Fig. 3 is a cross sectional view, taken along line A-A, of the cutting arrangement in Fig. 2.
Fig. 4 is a cross sectional view, taken along line B-B, of the cutting arrangement in Fig. 2.
Fig. 5 is a schematic view of a cutting arrangement according to a second embodiment.
Fig. 6 is a cross sectional view, taken along line A-A, of the cutting arrangement in Fig. 5.
Fig. 7 is an enlarged cross sectional view showing the groove 201.
Fig. 8 is a cross sectional view, taken along line C-C, of the cutting arrangement in Fig. 5.
Fig. 9 is a cross sectional view, taken along line B-B, of the cutting arrangement in Fig. 5.
Fig. 10 is an enlarged partial view of Fig. 8.
Fig. 11 is an enlarged partial view of a part of Fig. 9.
Fig. 12 is a schematic view of a cutting device for face cutting a groove side of the wood lamellae.
Fig. 13 is a cross sectional view, taken along line D-D in Fig. 12.
Fig. 14 is a cross sectional view of a finished wood lamella.
Figs 15a-15e schematically illustrate an alternative profiling system.
Figs 16a-16f schematically illustrate an alternative cutting system.

Detailed Description

Fig. 2 is a schematic side view of a device 10 for producing wood lamellae from a log 2. The device comprises a groove cutter 11 and a set 12 of radial cutters 121a, 121b, 121c, 121d and 121e. Moreover, the device 10 may comprise a conveyor arrangement 100a, 100b, 100c for causing relative movement between the log and the cutters 11, 12. Typically, the log may be moved relative to stationary cutters 11, 12. However, it is also possible to provide cutters 11, 12, which are capable of moving along the length of the log.
The log 2 has typically been longitudinally cut in half prior to being introduced into the device 10. That is, the log has been cut longitudinally along a plane containing a central axis C of the log. The log may have been pre-cut into an appropriate length, such as 1-10 m, preferably 1-5 m, 1-3 m or 1-2 m. Moreover, the log may have been wholly or partially debarked. Hence, the log can be said to present a planar surface 211 and a convex surface 210. For practical reasons, the log may be conveyed with its planar surface facing downwardly and oriented horizontally.
Fig. 3 is a cross sectional view taken along line A-A in Fig. 2. In Fig. 3, it is illustrated how the groove cutter 111 provides a longitudinal groove at the central portion of the log, i.e. at the pith area.
The groove cutter 111 may be formed as a circular, rotatable cutter having a cutting edge with a cross section that corresponds to a desired cross section of the groove 201.
The groove 201 formed by the groove cutter 111 presents a substantially concave surface 211' (Fig. 7, Fig. 9), which may be substantially half circular, or which may be polygonal, as seen in cross section in e.g. Fig. 7. In particular, the groove cutter may be adapted to provide a groove surface 211' having a polygonal cross section, with a number of straight portions which corresponds to the number of lamellae that are to be formed. In particular, one or more, preferably all, such straight portions may be substantially parallel with a respective corresponding outer surface that is to be formed in the ensuing step.
The groove cutter 111 may extend upwardly from a support on which the log is to be supported with its planar surface facing downwardly.
Fig. 4 is a cross sectional view taken along line B-B in Fig. 2. In Fig. 4, there is illustrated a set of radial cutters 121a, 121b, 121c, 121d, 121e. The cutters may be provided as circular saw blades having a respective axis of rotation 122a, 122b, 122c, 122d, 122e, which is perpendicular to the longitudinal direction of the log 2. Hence, each radial cutter 121a, 121b, 121c, 121d, 121e may define a plane, that contains a central axis C of the log.
Each radial cutter 121a, 121b, 121c, 121d, 121e may be individually driven, e.g. by a respective electric motor (not shown).
The radial cutters 121a, 121b, 121c, 121d, 121e may be arranged such that the log is divided longitudinally into a plurality of lamellae blanks 2', each having the cross sectional shape of a sector of a circle. Preferably, the cutters are placed such that the lamellae blanks 2' will have the same center angle a, which may be 60°, 45°, 36°, 30°, 22.5°, 18°, 15°, 12.9° or 11.25°, as desired.
Hence, the number of radial cutters may be 3, 4, 5, 6, 7, up to 15.
The radial cutters 121a, 121b, 121c, 121d, 121e extend from outside the outer convex surface 210 of the log 2 radially inwardly through the log and penetrating the groove surface 211', as can be seen in Fig. 11. Preferably, the radial cutters extend inwardly past the groove surface 211' by a distance which is less than the depth of the groove 201, preferably less than % of the depth, less than ½ of the depth or less than ¼ of the depth.
When feeding a log 2 through the device 10, with the planar surface 211 facing downwardly, the log 2 will initially engage the groove cutter 111, whereby a groove 201 is cut at a central portion of the log 2, in the pith area.
Subsequently, a guide device (not shown) may be introduced into the groove 201 and used for guiding the log when moving through subsequent machining arrangements.
Such a machining arrangement may be the set 12 of radial cutters 121a, 121b, 121c, 121d, 121e shown in Figs 2 and 4. When passing through the set 12, the log is divided into a plurality (here six) of lamellae blanks 2'.
The lamellae blanks 2' may then be machined into lamellae having trapezoidal cross section, e.g. as disclosed in US4122878 and as illustrated in Fig. 14. Optionally, a drying step, such as kiln drying, may be performed prior to such machining.
Figs 5-11 disclose another embodiment of a device 10' for producing wood lamellae having trapezoidal cross section.
Like in Figs 2-4, the device 10' comprises a groove cutter 111 and a set 12 of radial cutters. Hence, these need no further description.
Referring to Fig. 5, there is provided a scanning arrangement 13, which scans the log. Based on the scanning, a three dimensional model of the log may be provided, based on which the optimal way of cutting the log may be determined. The three dimensional model of the log may be based on a semi cylinder or a semi truncated cone. When scanning the log, its minimum radius may be identified and the model may be fitted to its outside with the aim at cutting away as little material as possible from the bark side of the log. As an option, limited areas of smaller radius may be tolerated, and optionally compensated for by a filling operation.
Referring to Figs 5, 8 and 10, there may be provided a set 14 of face cutters. This set may comprise a plurality of face cutters 141a, 141b, 141c, 141d, 141e, 141f, which may have the form of milling drums or profiler rolls, that are rotatable about an axis which extends substantially perpendicular to the longitudinal direction of the log 2. The face cutters may be positioned such that each face cutter has its effective cutting edge perpendicular to a line dividing the central angle a of the associated lamella (that is to be formed) into two.
The face cutters 141a, 141b, 141c, 141d, 141e, 141f may be moveable in the radial direction of the log 2. Hence, based on the data provided by the scanning arrangement 13, it is possible to control the face cutters 141a, 141b, 141c, 141d, 141e, 141f, such that each of them will cut a respective planar face 210' into the convex surface of the log, preferably while removing as little material as possible and thus saving as much as possible of the wood fibers at the outermost part of the log 2. Moreover, the face cutting may be performed such that longitudinal edges of adjacent planar faces 210' meet on a line where the radial cuts 203a, 203b, 203c, 203d, 203e are to be made.
Finally, the radial cutters 121a, 121b, 121c, 121d, 121e may engage the log 2 so as to cut it into a plurality of lamellae 2', as described with reference to Figs 2-4.
Hence, using the device 10' of Figs 5-11, it is possible to provide wood lamellae having approximately trapezoidal cross section, with three faces 210', 213a, 213b finished.
Moreover, if the groove cutter 11 is provided with the polygonal cross section and the sides of the polygon are provided to be parallel with the first base surfaces 210', it is possible to provide wood lamellae having all four faces finished.
As mentioned with reference to Figs 2-4, after the cutting step, the thus produced lamellae may be forwarded for further processing, such as further profiling to prepare them for producing e.g. a structure such as disclosed in Figs 1a-1c. Alternatively, the lamellae may be subjected to a drying step, such as through kiln drying. As yet another option, the lamellae may be stored until they are to be used.
Referring to Figs 12 and 13, there is disclosed a device 15 for finishing the fourth face of one or more wood lamellae produced according to the methods disclosed above.
The device 15 comprises a conveyor arrangement for conveying one or more lamellae. Moreover, the device comprises a guide surface 152a, 152b, 152c, 152d, 152e, 152f and a profiler 151a, 151, 151c, 151d, 151e, 151f.
The guide surface 152a, 152b, 152c, 152d, 152e, 152f may be adapted to interact with the surface of the lamella that was formed closest to the bark, i.e. the surface that was formed by the face cutters at section 14 in the device of Fig. 5, or the first, or major, base surface of the trapezoid that is to be formed.
The profilers 151a, 151, 151c, 151d, 151e, 151f may be adjustable in the direction normal to the guide surface, i.e. in the horizontal direction in Fig. 12. Hence, each profiler may be set to provide a lamella 20 having a fixed height as seen from the first base surface.
The device 15 may be arranged to process one lamella at the time, or it may process two or more lamella at the time in parallel, such as is indicated in Fig. 13.
For example, the device 15 may be arranged to process in parallel all of the lamellae 2' which were produced simultaneously during the cutting step at 12 in Fig. 2 or 5. For example, the lamellae output from the cutting step at 12 in Fig. 2 or 5 may be laid up side by side in the same order as the lamellae had when forming part of the log.
The device 15 may be arranged directly after the radial cutting device 12, with the lamellae being transported by a conveyor there between. As an option, a robot or an operator may handle the lamellae output from the cutting device 12 so as to position them correctly for the ensuing face cutting step at the device 15.
In Fig. 14, a cross section of a finished wood lamella is illustrated. The lamella presents the central angle a, a first base surface 210' formed at the portion of the log which is formed of the log portion closest to the bark, a second base surface 211", which is formed of the log portion closest to the pith. These two base surfaces are provided by the face cutters 141a-141f and 151a-151f, respectively. Extending between the base surfaces are the leg surfaces 213a, 213b provided by the radial cutters 121a-121e. The leg surfaces 213a, 213b are also planar.

Claims

A method of producing a plurality of wood lamellae having an approximately trapezoidal cross section, the method comprising:
providing a half log (2) having a semicircular cross section, presenting a convex surface (210) and a planar surface (211),

cutting a groove (201) at a central portion of the planar surface (211), such that the groove extends along a length direction (L) of the log (2), and

cutting at least two radial cuts (203a, 203b, 203c, 203d, 203e), each extending radially from the convex surface (210) to the groove (201) and along the length direction (L), such that at least three wood lamellae are formed.
The method as claimed in claim 1, further comprising scanning the log to determine at least one dimension of the log.
The method as claimed in claim 2, further comprising using the dimension for determining at least one of:
an intended position and extent of the groove (201), and

intended positions and extents of the radial cuts (203a, 203b, 203c, 203d, 203e).
The method as claimed in any one of the preceding claims,
wherein the at least two radial cuts (203a, 203b, 203c, 203d, 203e) are separated by an angle of 60°, 45°, 36°, 30°, 22.5°, 18°, 15°, 12.9° or 11.25°about a central axis (C) of the log.
The method as claimed in any one of the preceding claims,
wherein said at least two radial cuts (203a, 203b, 203c, 203d, 203e) are provided substantially simultaneously.
The method as claimed in any one of the preceding claims,
wherein the radial cuts (203a, 203b, 203c, 203d, 203e) extend past a surface of the groove by less than % of a maximum groove (201) depth, preferably less than ½ or less than ¼ of the groove depth.
The method as claimed in any one of the preceding claims, further comprising face cutting the convex surface (210), such that a first base surface (210') is provided, extending between intersections of the radial cuts and the convex surface (210).
The method as claimed in claim 7, further comprising following a line along the length direction (L) that is derived based on an outer surface of the log when face cutting the convex surface (210).
The method as claimed in claim 7 or 8, wherein the face cutting of the convex surface is performed before cutting the radial cuts (203a, 203b, 203c, 203d, 203e).
The method as claimed in any one of claims 7-9, further comprising face cutting the groove (201) surface, such that a second base surface (211") is provided, which is parallel to the first base surface (210').
The method as claimed in claim 10, further comprising following the first base surface (210') when face cutting the groove surface (211').
The method as claimed in claim 10 or 11, wherein the face cutting of the groove surface (211') is performed after cutting the radial cuts (203a, 203b, 203c, 203d, 203e).
A device for producing a plurality of wood lamellae having an approximately trapezoidal cross section, the device comprising:
a feed device (100a, 100b, 100c) for providing a log (2) having a semicircular cross section, presenting a convex surface (210) and a planar surface (211),

a groove cutter (11), arranged to cut a groove (201) at a central portion of the planar surface (211), such that the groove extends along a length direction (L) of the log,

at least two radial cutters (121a, 121b, 121c, 121d, 121e) each arranged to provide a radial cut (203a, 203b, 203c, 203d, 203e) extending from the convex surface (210) to the groove (211) and along the length direction (L), such that at least three wood lamellae are formed.
The device as claimed in claim 13, further comprising means (13) for scanning the log (2) to derive at least one dimension of the log (2).
The device as claimed in claim 13 or 14, further comprising a first face cutter (141a, 141b, 141c, 141d, 141e, 141f), arranged to cut into the convex surface (210) so as to provide a first base surface (210').
The device as claimed in claim 15, wherein the face cutter (141a, 141b, 141c, 141d, 141e, 141f) is moveable in a radial direction of the log, such that the cutting of the first base surface follows a line along the length direction (L) that is derived based on an outer surface of the log (2).
The device as claimed in any one of claims 13-16, further comprising a second face cutter (151a, 151b, 151c, 151d, 151e, 151f), arranged to cut into the groove surface (211') so as to provide a second base surface (211").
The device as claimed in claim 17, wherein the second face cutter (151a, 151b, 151c, 151d, 151e, 151f) is arranged to provide a constant distance between the first base surface (210') and the second base surface (211").