Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 0221~890 1997-10-02
A PROCESS FOR MAKING A WOOD
BOARD AND THE WOOD BOARD
FIELD OF THE INVENTION
The present invention relates generally to the art of
wood. More particularly, it concerns a process for making a
wood board from coniferous trees and the wood board produced
thereby.
BACKGROUND OF THE INVENTION
Coniferous trees such as black spruce, white spruce, red
spruce, grey pine, balsam fir and larch, because of their small
size, are traditionally known to produce low grade quality
lumber products such as wood chips or l"X3", l"X4" and l"X6"
boards. Uses of those coniferous trees for structural purposes
are very limited because of their inherent weakness. Presently,
the demand for those low-grade quality products is not as high
as the demand for high-grade quality and as can be easily
understood, the latter is a lot more profitable for producers.
Therefore, there is presently a need for a process that will
permit new, interesting and profitable uses for those
coniferous trees.
Known in prior art, there is US patent no 3,580,760 in the
name of Koch. This document describes a process for making a
laminated wood product utilizing modulus of elasticity
measurement. An object of this process is the making of high
strength laminates from boltwood trees which was then
considered a nonstructural material because of its small size
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and its relatively high proportions of juvenile wood. This
document teaches to arrange into a laminated structure the
laminae that have the greatest deflection in the center of the
structure and those with progressively less deflection located
away from the center. As can be easily understood, this process
is time-consuming and is not adapted to industrial production
of wood board.
Also known in prior art, there is US patent no 3,961,654
in the name of Hasenwinkle, that describes a process for making
a compo~ite lumber product from a generally cylindrical log.
The log is cut radially into a plurality of sector-shaped
pieces. These pieces are rejoined two by two, by bonding them
along opposed radial faces to form a parallelogram or a
rectangle. A plurality of those parallelograms or rectangles
are edge-bonded together into wider planar shapes. An object
of the invention described therein is to manufacture composite
lumber products that have improved quality.
Other examples of prior art related to the art of wood are
described in the following references:
3,580,760 May 25, 1971 P. Koch
3,961,654 June 8, 1976 Hasenwinkle
2,589,316 March 18,1952 A.M. Young
4,934,228 June 19, 1990 Bolton et al.
5,059,472 Oct.22,1991 Le Bell et al.
5,135,597 Aug.4, 1992 Barker
5,002,105 Mar. 26,1991 Bodig
1,778,333 Oct. 14, 1930 H. Neumann
2,942,635 June 28, 1960 R.C. Horne
5,648,027 Jul. 15, 1997 Tajiri et al.
4,496,421 Jan.29,1985 Byars et al.
3,908,725 Sept.30, 1975 Koch
CA 0221~890 1998-06-29
An object of the present invention is to propose a process
for making a wood board that satisfies the above-mentioned
needs. More particularly, an object of the present invention
is to propose a process for making a wood board from coniferous
trees, the board produced thereby showing excellent mechanical
characteristics.
Another object of the present invention is to provide a
process for making a high strength structural wood board from
coniferous trees which are traditionally considered as
nonstructural wood.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to a process
for making a wood board, the process comprising the steps of:
a) providing elongated pieces of wood each from a
coniferous tree and each preferably having a rectangular cross
section;
b) detecting an average fibre density of each of the
pieces of wood;
c) selecting among the pieces of wood those having an
average fibre density at least equal to a predetermined fiber
density which is preferably equal to 0,420 g/cm3;
d) planing off edges of the pieces of wood selected in
step c); and
e) bonding side by side the pieces of wood planed off in
step d) by means of their edges to form the wood board.
Preferably, prior to step d), the pieces of wood selected
in step c) are joined end to end to form a plurality of
lamellae of wood and in step e) those lamellae are bonded side
by side to form the wood board.
The coniferous tree is preferably selected from among
black spruce, white spruce, red spruce, grey pine, balsam fir
and larch. Most preferably, it is black spruce.
CA 0221~890 1998-06-29
Also preferably, the above process comprises after step
c), the additional step of removing any defect present in each
of the pieces of wood selected in step c).
The present invention also relates to a wood board
obtained by the process described above.
A further object of the present invention is to propose
a structural wood board (10) characterized in that it comprises
a plurality of edge-bonded pieces of wood (14) made of a
coniferous tree selected from among black spruce, white spruce,
red spruce, jack pine, balsam fir and larch, most preferably
from black spruce.
Among others, the present invention provides new
interesting and profitable uses for coniferous trees
traditionally known as nonstructural material. The present
invention also allows the quantity of wood required for any
construction to be reduced without affecting the strength of
the construction.
A non restrictive description of preferred embodiments of
the invention will now be given with reference to the appended
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a wood board according
to a preferred embodiment of the present invention; and
Figures 2a) to 2g) are each a perspective view of a wood
board according respectively to another preferred embodiment
of the present invention showing only an end portion of the
board.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to figure 1, a wood board (10) according to a
preferred embodiment of the present invention comprises a
plurality of lamellae of wood (12a and 12b) edge joined
CA 0221~890 1997-10-02
.
together. Depending on the length of the board (10) required,
each of the lamellae (12) preferably consist of a single pieces
of wood (14) as for lamellae (12a) or consist of a plurality
of pieces of wood (14), joined end to end in order to obtain
a desired length for each lamella, as for lamellae (12b).
In general, the thickness (t) of a wood board (10)
according to the present invention preferably varies
approximately between 1.25 to 3.00 inches, the width (w)
preferably varies between 1.50 to 96.00 inches and the length
(l) preferably vary between 48 to 720 inches. However, it
should be understood that a wood board according to the present
invention may have other dimensions than the ones above without
departing from the scope of the present invention.
Each lamella (12a,12b) preferably has a thickness
comprised between 1.25 to 3.00 inches, a width varying from 0.5
to 4.00 inches and a length varying from 48 to 720 inches.
The length of each piece of wood (14) preferably varies
from 8 to 96 inches.
Each piece of wood (14) comes from a coniferous tree and
has been specifically selected in order to make a wood board
of superior quality. This board shows uniform quality
throughout and may be used for structural purposes. More
particularly, only the pieces of wood (14) having at least a
predetermined average fibre density are selected and any defect
such as knots, blazes, blights, cracks, flaws or deviation
present in each of the pieces of wood (14) selected have
preferably been removed.
Each piece of wood (14) comes from a coniferous tree which
is preferably selected from among black spruce, white spruce,
red spruce, grey pine, balsam fir and larch. Most preferably,
the coniferous tree is the black spruce.
CA 0221~890 1998-06-29
In order to obtain a wood board that may compete with
lumber products traditionally used for structural purposes, the
average fiber density of each of the pieces selected is at
least equal to 0.420 g/cm3. It has been discovered that among
the pieces of wood coming from coniferous trees, the ones that
show the best mechanical properties are those coming from the
top of the tree or from stunted trees having a very slow
growing rate. Those small trees may reach 120 years, thereby
providing very close and dense fibers.
As already known in prior art, the mechanical properties
of a piece of wood is directly related to its fiber density.
Thus, selecting the pieces of wood according to their fiber
density, also means that the selection is made according to
their mechanical properties.
The lamellae (12) are joined edge to edge preferably by
means of glue. The glue used is preferably a structural wood
glue known in the art and may be selected from among pure
resorcinol and phenol-resorcinol-formaldehyde (PRF) or it may
be a nonstructural wood glue selected from among polyvinyl
acetate (PVA), urea melamine (UM) or urea formaldehyde.
The edges (16) of the lamellae (12) may be plane, as shown
in figure 1 or they may be profiled as shown in figures 2a) to
2g).
The profile is preferably selected from among a T-shaped
profile as in figure 2a), an obliquely-shaped profile as in
figure 2b), a squarely-shaped profile as in figure 2c), a
triangularly-shaped profile as in figure 2d), a circularly-
shaped profile as in figure 2e), a step-shaped profile as in
figure 2f) and a finger-shaped profile as in figure 2g).
When the lamellae (12) are formed from a plurality of
pieces of wood (14) joined end to end, those pieces (14) are
preferably finger-jointed by means of glue as shown in
figure 1. Finger jointing is already known in prior art and
does not require further explanation.
CA 0221~890 1997-10-02
BEST MODB OF REALIZATION OF A PROCESS ACCORDING TO THE PRESENT
INVENTION
The process for making a wood board (10) as described
above comprises the steps of:
a) providing elongated pieces of wood (14) each from a
coniferous tree and each having a rectangular cross section;
b) detecting an average fiber density of each of the
pieces of wood (14);
c) selecting among the pieces of wood (14) those having
an average fiber density at least equal to a predetermined
fiber density;
d) planing off edges of the pieces of wood (14) selected
in step c); and
e) bonding side by side the pieces of wood (14) planed off
in step d) by means of their edges (16) to form the wood board.
In step e), the pieces of wood (14) are preferably edge-
glued together by using an appropriate wood glue as described
hereinbefore.
Preferably, if any piece of wood (14) selected in step c)
is not long enough, for example if its length is less than
4 feet, the process comprises, prior to step d), an additional
step of jointing end to end said pieces of wood (14) to form
a plurality of lamellae of wood (12) and in step e) those
lamellae (12) are bonded side by side to form the wood board
(10). The jointing is preferably made with a finger-joint using
an appropriate wood glue.
AS mentioned before, in order to make a wood board (10)
that may compete with traditional structural lumber products,
the predetermined fiber density is approximately 0,420 g/cm3.
CA 0221~890 1997-10-02
Preferably, the process comprises, after step c), the
additional step of removing any defect present in each of the
pieces of wood (14) selected in step c).
The selection of the appropriate pieces of wood (14) is
obtained by means of an electronic system which can first
detect the fiber density at different locations along each
piece of wood (14) passing through the system and then
calculate the average fiber density of each of said pieces of
wood (14). Preferably, the electronic system is adapted to
detect any defect present in each of the pieces of wood (14)
and to remove those defects therefrom.
The process may comprise, prior to step d) of planing off,
a step of profiling edges (16) of the pieces of wood (14) as
described hereinbefore and as shown in figures 2a) to 2g).
In order to obtain a wood board (10) of a given width, the
process preferably comprises, after step e) of bonding side by
side the pieces of wood (14), an additional step of taking off
sides of the wood board.
The sequence of steps for making a wood board (10)
according to a preferred embodiment of the invention from the
reception of the raw material to the final product may be the
following:
- reception of the dry raw material which consists of a
plurality of pieces of wood coming from different
varieties of coniferous trees;
- stock piling the raw material;
- feeding the raw material to the mill;
- preheating the raw material;
- detection of the average fiber density of each of the
pieces of wood;
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- selection of the pieces of wood having an average fiber
density at least equal to 0,420 g/cm3;
- detecting and eliminating any defect present in each
piece of wood;
- profiling the end joints;
- applying the glue on the profiles made;
- end jointing the pieces of wood and pressing the joints
to form lamellae of wood;
- hardening of the glue joints;
lo - precision planing off of the lamellae;
- application of glue on the edges of the lamellae;
- edge bending the lamellae and pressing the lamellae to
form a wood board;
- hardening of the edge joints of the board;
- trimming sides of the board to a desired width;
- precision planing off of the board;
- trimming ends of the board with precision;
- piling and wrapping of the final product;
- stocking the final product; and
- shipping the final product to the client.
As mentioned before, a wood board according to the present
invention shows surprisingly improved mechanical properties.
If each of the pieces of wood is selected such that its average
fibre density is at least equal to 0,420 g/cm3, the wood board
produced therefrom according to the present invention may
compete with any traditional structural lumber products. The
following table I shows the mechanical properties of a wood
board EGB(edge glued board) according to the present invention
which has been tested in laboratory and the mechanical
properties of conventional and engineered lumber product of the
CA 0221~890 1997-10-02
same size. The EGB mentioned therein comprises a plurality of
edge glued pieces of wood, each free from any defect and having
an average fiber density at least equal to 0,420 g/cm3.
TABLE I
Mechanical properties of a wood board according to the present
invention as compared to conventional and engineered lumber
products.
LUMBER MODULUS OF FLEXURAL TENSILE COMPRESSIVE
PRODUCT ELASTICITY STRENGTH STRENGTH STREN6TH
(Spruce, (MPa) (E) ~Fb) (MPa) (MPa)
Pine,Fir) (MPa) (F) (Fc)
No.2 8,965 6.9 4.1 4.7
Grade
No. 1 10,345 8.3 5.0 6.0
Grade
MSR* 11,025 12.4 8.1 10.0
1800
MSR* 12,405 14.5 10.9 11.7
2100
LVL* 13,790 20.2 13.8 20.9
Parallam* 13,790 21.4 16.5 20.0
Gang- 13,790 37.6 27.9 38.8
Lam* LVL
EGB 13,350 55.4 50.9 37.3
Trade-marks MPa
CA 0221~890 1997-10-02
As can be appreciated, the wood board obtained according
to the present invention shows mechanical properties superior
or equal to any known structural lumber product.
Therefore, a wood board according to the present invention
may have many different uses in a framework. For example, it
may be used as a frame wall, as a composing element of a truss,
as a composing element of a floor beam, as a composing element
of a laminated beam or as a joist.
As the raw material used in the making of a board
according to the present invention comes from coniferous tree
and most preferably from black spruce which are traditionally
used for the production of wood chips or low grade quality
boards, this invention will provide a new interesting market
for these trees.
Although preferred embodiments of the invention have been
described in detail herein and illustrated in the accompanying
drawings, it is to be understood that the invention is not
limited to these precise embodiments and that various changes
and modifications may be effected therein without departing
from the scope,of the present invention.
