Method of producing a laminated wood product, and laminated wood products

Abstract

The present disclosure provides a method of forming a laminated wood product, which is adapted for receiving a load in a direction perpendicular to a principal fiber direction of the wood. The method comprises cutting a log (2) along the principal fiber direction of the log, into a plurality of wood lamellae (20a, 20b), such that the wood lamellae are formed as radial sections of the log, forming the wood lamellae (20a, 20b) to provide each wood lamella with a trapezoidal cross section, whereby the wood lamellae present a respective planar major base surface (bs1) that is formed at a radially outer part of the log (2) and a respective planar minor base surface (bs2) that is formed at a radially inner part of the log (2), arranging the lamellae (20a, 20b) as at least one layer in which planar major base surfaces (bs1) of immediately adjacent lamellae (20a, 20b) face opposite directions, and gluing together the lamellae (20a, 20b) side surface to side surface (ss1, ss2) such that a wood billet is formed. The method further comprises arranging the wood lamellae (20a, b) such that the major base surfaces (bs1) of immediately adjacent wood lamellae taper in opposite directions, and the gluing comprises wet gluing.

Claims

1. A method of forming a laminated wood product, which is adapted for receiving a load in a direction perpendicular to a principal fiber direction of the wood, the method comprising: cutting a log along the principal fiber direction of the log, into a plurality of wood lamellae, such that the wood lamellae are formed as radial sections of the log, forming the wood lamellae to provide each wood lamella with a trapezoidal cross section, whereby the wood lamellae present a respective planar major base surface that is formed at a radially outer part of the log and a respective planar minor base surface that is formed at a radially inner part of the log, and to provide each wood lamella with a taper in the principal fiber direction, arranging the lamellae as at least one layer in which planar major base surfaces of immediately adjacent lamellae face opposite directions, and gluing together the lamellae side surface to side surface such that a wood billet is formed, wherein the arranging step includes arranging the wood lamellae by turning every second lamella about 180 about an axis perpendicular to the principal fiber direction of the wood and perpendicular to the major base surface such that the major base surfaces of immediately adjacent wood lamellae taper in opposite directions, and wherein the gluing step comprises wet gluing at a moisture content of the wood lamellae greater than 25% by dry mass.

2. The method as claimed in claim 1, wherein the forming comprises a first forming step, in which the major base surfaces are formed along the outermost part of the log, along a direction which is substantially parallel with the outermost surface of the log.

3. The method as claimed in claim 1, wherein the minor base surfaces are formed along a direction which, as seen in a plane containing the pith, presents an angle relative to a pith direction, that is greater than an angle between the major base surface and the outermost surface of the log.

4. The method as claimed in claim 1, wherein the forming comprises a second forming step, in which the minor base surfaces are formed by removal of material at a portion of the respective lamella, which is close to the pith, and wherein more of a height of the trapezoidal cross section is removed when forming the minor base surface than when forming the major base surface.

5. The method as claimed in claim 1, wherein the wood lamellae are formed such that a distance, along a surface normal of the base surfaces, between the base surfaces, is at least 50% of a radius of the log.

6. The method as claimed in claim 1, wherein the cutting comprises cutting the wood lamellae to an apex angle of less than 45.

7. The method as claimed in claim 1, further comprising a step wherein said wood lamellae are subjected to surface drying prior to gluing the wood lamellae together.

8. The method as claimed in claim 7, wherein the surface drying affects the moisture content of the wood lamellae by less than 5%.

9. The method as claimed in claim 1, wherein arranging the lamellae comprises arranging the lamellae as a single layer, with base surfaces exposed.

10. The method as claimed in claim 1, further comprising cutting the billet along a plane which is parallel to the principal fiber direction, and perpendicular to the base surfaces, thus forming a plurality of planks.

11. The method as claimed in claim 10, further comprising subjecting the planks to a drying step.

12. A method of forming a laminated wood product, which is adapted for receiving a load in a direction perpendicular to a principal fiber direction of the wood, the method comprising: cutting a log along the principal fiber direction of the log, into a plurality of wood lamellae, such that the wood lamellae are formed as radial sections of the log, forming the wood lamellae to provide each wood lamella with a trapezoidal cross section, whereby the wood lamellae present a respective planar major base surface that is formed at a radially outer part of the log and a respective planar minor base surface that is formed at a radially inner part of the log, arranging the lamellae as at least one layer in which planar major base surfaces of immediately adjacent lamellae face opposite directions, and gluing together the lamellae side surface to side surface such that a wood billet is formed, wherein the arranging step includes arranging the wood lamellae such that the major base surfaces of immediately adjacent wood lamellae taper in opposite directions, wherein the gluing step comprises wet gluing at a moisture content of the wood lamellae greater than 25% by dry mass, cutting the billet along a plane which is parallel to the principal fiber direction, and perpendicular to the base surfaces, thus forming a plurality of planks, subjecting the planks to a drying step, and joining together at least two of the dried planks in an end-to-end manner, such that a longer plank is formed.

13. A method of forming a laminated wood product, which is adapted for receiving a load in a direction perpendicular to a principal fiber direction of the wood, the method comprising: cutting a log along the principal fiber direction of the log, into a plurality of wood lamellae, such that the wood lamellae are formed as radial sections of the log, forming the wood lamellae to provide each wood lamella with a trapezoidal cross section, whereby the wood lamellae present a respective planar major base surface that is formed at a radially outer part of the log and a respective planar minor base surface that is formed at a radially inner part of the log, arranging the lamellae as at least one layer in which planar major base surfaces of immediately adjacent lamellae face opposite directions, and gluing together the lamellae side surface to side surface such that a wood billet is formed, wherein the arranging step includes arranging the wood lamellae such that the major base surfaces of immediately adjacent wood lamellae taper in opposite directions, wherein the gluing step comprises wet gluing at a moisture content of the wood lamellae greater than 25% by dry mass, cutting the billet along a plane which is parallel to the principal fiber direction, and perpendicular to the base surfaces, thus forming a plurality of planks, and laminating together at least two planks by gluing base surface to base surface.

14. The method as claimed in claim 1, wherein the gluing comprises wet gluing, i.e. gluing at a moisture content of the wood lamellae greater than 30% by dry mass.

15. The method as claimed in claim 1, wherein the wood lamellae are formed such that a distance, along a surface normal of the base surfaces, between the base surfaces, is at least 70% of the radius of the log.

16. The method as claimed in claim 1, wherein the cutting comprises cutting the wood lamellae to an apex angle of less than or equal to 36.

17. The method as claimed in claim 7, wherein the surface drying affects the moisture content of the wood lamellae by less than 1%.

18. The method as claimed in claim 10, further comprising laminating together at least two joined-together planks by gluing base surface to base surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1a-1k schematically illustrate a method of making a laminated wood product.

(2) FIG. 2a is a schematic side view of a system for producing wood lamellae

(3) FIG. 2b is a schematic sectional view taken along line A-A of FIG. 2a.

(4) FIGS. 3a-3c schematically illustrate an alternative method of processing the intermediate wood product provided in FIG. 1h.

(5) FIGS. 4a-4c schematically illustrate yet another alternative method of processing the intermediate wood product provided in FIG. 1h.

DETAILED DESCRIPTION

(6) FIG. 1a schematically illustrates a log 2, which has been cut longitudinally into two halves 2. The log 2 may have been debarked prior to this cutting. The cutting may be performed by any type of cutting device, such as, but not limited to, a saw, e.g. a circular saw or a band saw.

(7) FIG. 1b schematically illustrates a log half 2 after it has provided with a longitudinally extending groove 23 along its pith and cut longitudinally into six radial sections 2a, 2b, as will be further described with reference to FIGS. 2a-2b.

(8) FIG. 1c schematically illustrates processing of one of the radial sections 2a, 2b, into a lamella 20a, 20b. The lamella 20a, 20b is subjected to forming of base surfaces bs1, bs2, to form a lamella 20a, 20b, which will present a trapezoidal cross section.

(9) The base surfaces bs1, bs2 thus formed comprise a major base surface bs1, which is formed by tool 31 closest to the bark of the log and along the bark side. The base surfaces further comprise a minor base surface bs2, which is formed close to the pith and parallel with the major base surface bs1 by tool 32.

(10) The tools 31, 32 may be any type of tool capable of forming a planar surface, including but not limited to milling cutters, circular saw blades or band saw blades.

(11) The first tool 31, which forms the major base surface bs1, is arranged to use the bark side as reference, such that the major base side bs1 is formed along a direction parallel with the bark side.

(12) The second tool 32, which forms the minor base surface bs2, is arranged to use the major base surface and/or the bark side as a reference, such that the minor base surface bs2 is formed along a direction parallel with the major surface and/or the bark side.

(13) The cross section of the lamellae 20a, 20b is trapezoidal having a constant height. With the major base surface bs1 being formed substantially parallel with the bark, and with the log presenting a frusto-conical shape, it is recognized that the major base surface bs1 will taper along the central direction of the log C. That is, the log will taper in a direction towards the top of the tree from which it was formed. This direction is also parallel with the principal fiber direction of the log and of the wood lamellae.

(14) Moreover, the minor base surface bs2 will also taper along the central direction C of the log.

(15) The fact that the radius of the log would also diminish towards the top of the tree from which it was formed, implies that while the amount of material removed at the bark side, by tool 31, in the forming of the major base sides bs1 will be substantially constant along the length of the lamella 20a, 20b, as seen in the radial direction.

(16) However, the amount of material removed at the pith side, by tool 32, will diminish towards as seen in the direction towards the top of the tree from which the lamella 20a, 20b was formed.

(17) Referring to FIG. 1d, after the lamellae 20a, 20b have been formed, each lamella will have a major and a minor base surface bs1, bs2 and a pair of side surfaces ss1, ss2, which will be identical.

(18) Referring to FIG. 1e, every second lamella 20b will now be turned or flipped about 180 about its longitudinal axis and about 180 about an axis perpendicular to the longitudinal axis and perpendicular to the major base surface bs1, such that the lamellae will become positioned as illustrated in FIG. 1e. That is, the directions of taper Ca and Cb will extend in opposite directions.

(19) At this point, the base surfaces of every pair of adjacent wood lamellae 20a, 20b will taper towards substantially opposite directions. Moreover, major base surfaces bs1 of every pair of adjacent wood lamellae will face substantially opposite directions, i.e. one upwards in FIG. 1e and the other one downwards in FIG. 1e.

(20) At this point, the wood may still be wet, that is, its moisture content may be more than 25% by dry mass, preferably more than 30%. Hence, the wood has not been subjected to any accelerated or intentional drying, such as kiln drying.

(21) The lamellae may then be wet glued together side surface to side surface. Such wet gluing may be made without the cut surface, i.e. the side surfaces, being subjected to any further surface processing other than cleaning and removal of free water from the cut surface.

(22) When wet gluing, it is recommended to reduce the amount of free water on the wood surface to a minimum. Hence a brief surface drying step, basically having no effect except for on the very surface, may be performed, e.g. by means of a fan.

(23) FIG. 1f schematically illustrates the two lamellae 20a, 20b when arranged adjacent each other, side surface ss1 to side surface ss2 and with base surfaces bs1, bs2 of the pair of thus adjacent lamellae 20a, 20b tapering in opposite directions.

(24) Referring to FIG. 1g, there is illustrated a pair of glue applicators 33a, 33b, which apply glue to side surfaces of lamellae 20a, 20b, respectively. A single, or even more, glue applicators may be used.

(25) The lamellae are then arranged as illustrated in FIG. 1g, i.e. with the base surfaces bs1, bs2 of every pair of adjacent wood lamellae 20a, 20b tapering towards substantially opposite directions and major base surfaces bs1 of every pair of adjacent wood lamellae facing substantially opposite directions.

(26) The glue used is a glue adapted for wet gluing wood, such as a water activated glue. One example of such glue is a polyurethane (PU) based glue.

(27) The lamellae 20a, 20b will be subjected to a pressing tool 34 pressing the lamellae 20a, 20b together in directions perpendicular to the base surfaces 20a, 20b and/or parallel with base surfaces 20a, 20b and perpendicular to longitudinal axes C.

(28) FIGS. 1h-1k schematically illustrate a first way of processing the billet 200.

(29) As illustrated in FIG. 1h, after the gluing process, an intermediate wood product, here referred to as a billet 200 is provided, made up of wood lamellae 20a, 20b glued together first side surface ss1 to first side surface ss1 and second side surface ss2 to second side surface ss2.

(30) In the illustrated example, the billet 200 consists of a single layer of lamellae 20a, 20b, which are arranged side surface to side surface and with major base surfaces bs1 of immediately adjacent lamellae facing opposite directions and with base surfaces bs1, bs2 of immediately adjacent lamellae tapering in width in opposite directions.

(31) Referring to FIG. 1i, the billet 200 may be divided by cuts 2012 into a plurality of wood pieces 201 having substantially rectangular or square cross section and being of desired dimensions. These cuts 2012 may extend in planes that are perpendicular to the base surfaces and parallel with the principal fiber direction C of the lamellae 20a, 20b.

(32) Each wood piece 201 will consist of parts of at least two lamellae 20a, 20b, frequently of three or more lamellae, which are arranged such that base surfaces bs1, bs2 every pair of adjacent wood lamellae 20a, 20b taper towards substantially opposite directions and major base surfaces bs1 of every pair of adjacent wood lamellae face substantially opposite directions. At least one of the wood lamellae 20a, 20b may present an incomplete trapezoidal cross section. The planks 201 may have a width corresponding to 1-3, preferably 1-2 major base surfaces of the lamellae 20a, 20b it is made up of. Moreover, the planks may have a thickness which is more than 50% of the radius of the log from which the lamellae were formed, preferably more than 75% of such radius, more than 80% of such radius, more than 85% of such radius or even more than 90% of such radius.

(33) Referring to FIG. 1j, the wood pieces 201 may then be subjected to an accelerated drying, such as kiln drying, so as to reduce their moisture content to less than 20% by dry mass, preferably less than 15% by dry mass or less than 10% by dry mass.

(34) Referring to FIG. 1k, a pair, or more of the dried wood pieces 201 may be provided with a joint, such as a finger joint 202, such that a plank of a desired length is provided, after which they can be used as construction material.

(35) Such wood pieces or planks may be further formatted, such as planed on one or more sides thereof and/or profiled.

(36) Areas of use for such wood pieces or planks include primarily structural members, such as joists, beams, studs or pillars.

(37) FIG. 2a is a schematic side view of a device 300 for producing wood lamellae 20a, 20b from a half-log 2. The device comprises a groove cutter 311 and a set 312 of radial cutters 321a, 321b, 321c, 321d and 321e. Moreover, the device 300 may comprise a conveyor arrangement 300a, 300b, 300c for causing relative movement between the log and the cutters 311, 312. Typically, the log may be moved relative to stationary cutters 311, 312. However, it is also possible to provide cutters 311, 312, which are capable of moving along the length of the half-log 2.

(38) The half log 2 has typically been longitudinally cut in half prior to being introduced into the device 300. 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 22 and a convex surface 21. For practical reasons, the log may be conveyed with its planar surface facing downwardly and oriented horizontally.

(39) FIG. 2b is a cross sectional view taken along line A-A in FIG. 2a. In FIG. 2b, it is illustrated how the groove cutter 311 provides a longitudinal groove at the central portion of the log, i.e. at the pith area.

(40) The groove cutter 311 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 23.

(41) The groove 23 formed by the groove cutter 311 may presents a substantially concave surface, which may be substantially half circular, or which may be polygonal.

(42) The groove cutter 311 may extend upwardly from a support on which the log is to be supported with its planar surface 22 facing downwardly.

(43) FIGS. 3a-3c schematically illustrate another way of processing the billet 200 formed at FIG. 1g and illustrated in FIG. 1h.

(44) FIG. 3a illustrates a cutting scheme which differs from that disclosed with respect to FIG. 1i. Here the vertical cuts 2012, i.e. cuts extending substantially parallel with a principal fiber direction of the lamellae 20a, 20b and perpendicular to the base surfaces bs1, bs2 have a greater spacing, such that wider planks 201 are provided.

(45) Moreover, there is illustrated a horizontal cut 2013, i.e. a cut extending substantially parallel with a principal fiber direction of the lamellae, but parallel with the base surfaces bs1, bs2.

(46) Based on one or more horizontal cuts 2013, it is possible to divide the billet into two or more sheets, and/or it is possible to provide planks having smaller thickness. Each such plank 201 will then be formed of parts of two or more lamellae having trapezoidal cross section.

(47) However, while the cutting illustrated in FIG. 1i provides wood pieces or wood planks 201 having a width corresponding to 1-2 major base surfaces bs1, the planks 201 provided in the sawing according to FIG. 3b may have a width of 2-6 major base surfaces bs1, preferably 2-4 major base surfaces bs1.

(48) At this point, the planks 201 may be subjected to an accelerated drying process, such as kiln drying, as described with respect to FIG. 1j.

(49) Before, or after the drying, planks 201 may be joined in an end-to-end manner, as described with respect to FIG. 1k, thus forming extended planks.

(50) FIG. 3b schematically illustrates a process of gluing together such planks 201 and/or extended planks base surface to base surface by applying glue to the base surfaces. Such gluing may be a dry gluing.

(51) In FIG. 3b, there is illustrated a glue applicator 36 which applies glue to the surface of the wood pieces 201 (and/or finger jointed beams/planks) that is formed by the base surfaces bs1, bs2. The wood pieces 201 are then glued together base surface bs1, bs2 to base surface bs1, bs2 as illustrated in FIG. 3b.

(52) The wood pieces may be subjected to a pressing tool 37 pressing them together in directions parallel to the base surfaces and/or perpendicular to base surfaces and perpendicular to longitudinal axes C.

(53) A predetermined number of wood pieces 201 or planks may be glued together in this manner to form e.g. a glulam beam 205.

(54) FIG. 3c schematically illustrates such a glulam beam 205, which has been formed by the process described with respect to FIGS. 3a-3c. That is, the beam 205 is formed by a plurality of layers, which each comprise lamellae 20a, 20b having trapezoidal cross section, which are glued together side surface to side surface. The layers are glued together base surface to base surface. The layers may have substantially equal thickness, that is equal thickness +/ less than 10%, preferably +/ less than 5% or +/ less than 2%. Each layer may have a thickness which is 50% or less of a radius of a log from which the lamellae making up the layers were formed, possibly 40% or less or 30% or less.

(55) FIGS. 4a-4c schematically illustrate yet another way of processing the billet 200 formed at FIG. 1g. Here, just like in FIG. 1i, the billet 200 is cut along the length direction C, perpendicular to the base surfaces and along the principal fiber direction of the wood lamellae 20a, 20b, into a plurality of wood pieces 201, by a saw 35, as illustrated in FIG. 4a. The saw may be of the same type as the saw used for the cutting outlined with respect to FIG. 1i.

(56) However, while the cutting illustrated in FIG. 1i provides wood pieces or wood planks 201 having a width corresponding to 1-2 major base surfaces bs1, the planks 201 provided in the sawing according to FIG. 4b may have a width of 2-6 major base surfaces bs1, preferably 2-4 major base surfaces bs1 and a thickness which is more than 50% of the radius of the log from which the lamellae were formed, preferably more than 75% of such radius, or even more than 90% of such radius.

(57) After this cutting step, the thus produced wood pieces 201 may be subjected to accelerated drying, e.g. kiln drying, in the same manner as was described with respect to FIG. 1j.

(58) After the drying step, it is possible to finger joint wood pieces 201 to form beams or planks of a desired length, as was described with reference to FIG. 1k.

(59) Optionally, the planks 201 may be formatted, such as planed on one or more sides, before or after the finger jointing step.

(60) In FIG. 4b, there is illustrated a glue applicator 36 which applies glue to the surface of the wood pieces 201 (and/or finger jointed beams/planks) that is formed by the base surfaces bs1, bs2. The wood pieces 201 are then glued together base surface bs1, bs2 to base surface bs1, bs2 as illustrated in FIG. 4b.

(61) The wood pieces 201 are subjected to a pressing tool 37 pressing them together in directions parallel to the base surfaces and/or perpendicular to base surfaces and perpendicular to longitudinal axes C.

(62) A predetermined number of wood pieces 201 or planks may be glued together in this manner to form e.g. a glulam billet 206.

(63) The glulam billet 206 may be used as is, or, it may be cut into one or more beams 207 as illustrated in FIG. 4c. That is, the billet 206 comprising lamellae 20a, 20b having trapezoidal cross section, that are glued together both side surface to side surface and base surface to base surface, may be cut along plane that is parallel to the base surfaces and with the principal fiber direction of the wood lamellae 20a, 20b. Such a beam 207 may comprise at least two layers, preferably 2-5 layers, that have substantially the same thickness and one or two layers having a smaller thickness, e.g. having a thickness which is 70% or less than the thickness of the other layers, or even 50% or less or 30% or less.