Note: Descriptions are shown in the official language in which they were submitted.
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CA 02434248 2003-07-03
2
TECHNICAL FIELD
The present invention is directed to a method of producing mufti-ply solid
wood panels from
balsam fir and similar woods in terms of mechanical properties, wherein the
mufti-layered
product comprises thin boards obtained from standard lumber products by the
utilization of thin
sawing method.
BACKGROUND
Current construction challen, es:
~ Sound transmission:
o Poor sound insulation of traditional systems consisting of one layer of
plywood not
fastened with glue.
o Specific problem with high frequency sounds and resonance associated with
hardwood floors.
~ Dimensional stability:
o Dimensional stability problem with one layer floors, in particular at the
joints.
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Rigidity:
o Current sub flooring made up of one layer of plywood or OSB panels do not
possess
sufficient rigidity or stiffness as a sub-floor for rigid flooring material
such as
hardwood flooring, engineered wood flooring, ceramic tiles and others.
o Traditionally with the limitations of plywood in standard panels dimensions
(4 feet x
8 feet and thicknesses between 5/8" and '/4") architects and builders must
maintain a
reduced spacing between the joists, in some cases as little as 12 inches.
Builders current solutions:
~ Fastening utilizing glue and screws between the sub-flooring and the joists.
~ Installation of a second layer of plywood panel over the first utilizing
screws and glue all
the while staggering the joints to enhance the homogeneity and the dimensional
characteristics of the surface.
Typically, one layer of sub-flooring of plywood or OSB panels is installed on
the first
floor of a residence where hardwood flooring is to be installed.
Where ceramic tile is installed on the first floor of a residence, a thin
plywood panel
overlay is installed over the single layer sub-floor in order to assure
rigidity and
homogenous surface.
Another alternative is the application of a light coat of ciment over the one
layer sub-
floor as long as the sub-floor in question has the necessary rigidity /
stiffness to accept
the ciment.
Challenges with builders current solutions:
~ Additional labor required for second layer of plywood panels.
~ Sound insulation is now in relation to the total mass of the sub-floor.
However the
additional weight of the sub-floor in question can create a trampoline effect.
~ Incorrect use of the double layer sub- floor in a residence, where double
layer is only
used for leveling purpose for hardwood flooring and ceramic tiles. This
application gives
unsatisfactory results where large dimension ceramic tiles are to be utilized.
Modular solution principle:
~ A panel designed in relation to a modular system for flooring which presents
an
integrated solution to builders challenges relative to sub-flooring as
follows:
o Installation utilizing one layer instead of two.
o Ease of installation with respect to the use of screws and glue.
o Increased rigidity / stiffness allowing more latitude for joists spacing.
~ Contributes to better sound insulation against high frequency sounds by use
of this
modular sub-flooring due to the increased thickness and lighter density of the
material.
Of note the contribution of the sub-floor to sound insulation is however
minor.
~ Homogenous surface permitting the utilization of large dimension ceramic
tile ( a light
overlay however could still be required to even out the hardwood flooring.
~ Increased resistance to fire due to the additional thickness.
~ Dimensional stability with respect to changes in humidity levels due to a
factory applied
sealer.
~ In modular flooring material, mechanical resistance is not the only
important element;
the possibility of increased thickness while maintaining light weight becomes
an
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CA 02434248 2003-07-03
advantage as it reduces the total mass of the flooring. The builders therefore
have more
latitude with respect to more efficient sound insulation systems and materials
(i.e.
double gypsum-board, insulation, etc.).
Therefore the present concept constitutes an original solution to a non
evident integrated
harmonization of flooring since it provides a new approach to construction
methods
which have not evolved significantly from plywood panels or other materials
available
in standard dimensions for sub-flooring use.
Disparity problems with SPFL (spruce, pine, fir larch) wood species
~ Considered as a whole, the SPFL wood species is difficult to assess as an
engineered
material due to varying mechanical properties. The basic densities at 12%
moisture
content vary between species from 0,34 gr/cm' to 0,49 gr/cm3, and longitudinal
shearing
varies from 58,3 MPA to 78,3 MPA (Jessome 1977).
Therefore from a mechanical strength perspective, it is necessary to consider
the SPFL
species in a distinct fashion as follows:
o Black spruce, which constitutes the reference point for softwood mechanical
resistance of which larch can also be included.
o Balsam fir and white spruce which distinguish themselves by their light
weight.
Particularities of balsam fir:
~ The characteristics of balsam fir presented a major limitation to its use
until this present
integrated solution proposal:
o Lightness. The basic density of balsam fir is 0,335 gr/cm'.
o Strong moisture content. When at a green state, balsam fir has a moisture
content
generally in excess of 80% which is often captured in water pockets.
o Structural limits. The longitudinal shearing limit of balsam fir is 58,3
MPA, which is
approximately 25% less than black spruce (Jesson 1997).
Balsam fir / white spruce solution:
~ Therefore, there exist an opportunity to introduce balsam fir and white
spruce in
lightweight material market segment in order to:
o Make available a material of less density which has the capability of
absorbing high
frequency sounds. Balsam fir has an average density that is lower than all
wood
species currently being utilized for plywood panel manufacturing.
o Increase the sub-flooring thickness to obtain increased rigidity / stiffness
all the while
reducing its weight; this cannot be accomplished with the current species
utilized in
plywood panels.
o In order to benefits from the better plastic properties of lighter density
woods when
exposed to humidity changes it becomes evident that the lesser density wood
will be
subject to less internal stresses I cracking in a panel (confirmed by
testing).
Solution based on manufacturing of face- 1g ued panels:
~ The face gluing of thin sawn wood targets the same objective as plywood
panels which
is a stabilized panel. It is virtually impossible to obtain similar stability
in a one layer
panel.
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CA 02434248 2003-07-03
~ There exists an area of development for utilization of thin sawing
principles in stabilized
panel manufacturing, due to the following
o In order to increase the length and reduce the width of panels to obtain a
more
homogenous flooring surface as a whole. This cannot be accomplished with
plywood
panels in current manufacturing facilities since rotary slicing equipment
generally
operates with a maximum length of 2,5 meters, hence a maximum for panel
length.
~ The face-gluing techniques opens perspectives in the same market segment:
o Potential for a niche product made up of a total integrated panel including
the
possibility of a hardwood overlay/layer.
o Potential of a panel with appearance features including an overlay/layer of
wood
species such as larch.
o Potential for the manufacturing of the same panel but utilizing aspen or
poplar
(increased density).
Ecological solution:
~ The face gluing solution enables a better utilization of raw materials in a
high value
added integrated product.
~ Potential for high quality woods use in overlay/layer for appearance on the
panel faces,
the other lesser grade woods would be utilized in the internal layers of the
panel.
~ In this integrated solution, the softwood wood species can therefore aspire
to a longer
economic life in a construction environment, in comparison to a utilization
for crating or
material handling.
A process based on high precision:
1. The wood is procured in a green state or kiln dried as per current practice
to 19% moisture
content (Figure 1 - Item 1). The desired lumber dimension is 1.7 inches in
thickness by 2.7,
3.7 or 5.7 inches in width (actual dimensions). The lengths will be procured
from 4 foot
and more, graded or not graded.
2. Outside storage of the wood in a green state is recommended (Figure 1 -
Item 2). It must
be in a well ventilated storage area to air dry the wood and stabilize the
moisture content.
3. Drying to a 6-8% moisture content in pre-drying kiln utilizing low
temperature to reduce
wood degradation to a minimum (Figure 1 - Item 3). This degradation is
frequent in SPFL
species when moisture content reach levels inferior to 10% with conventional
high
temperature drying techniques. The first stage of drying for this application
must utilize
the principle of saturating the atmosphere in the kiln with water vapor in
order to enhance
the moisture content internal equilibrium of the wood.
4. Selection and stacking by category of the wood components utilized in the
different parts
of the panel. The lesser quality components will be utilized in the middle or
the lower
non apparent section of the panel (Figure 1 - Item 5).
5. Sawing with ultra-thin saws enabling immediate face-gluing (an alternative
would be
slicing if new thick slicing techniques permit immediate gluing). The thin
board
thicknesses vary between 0,31 and 0,75 inches. The ultra-thin saws permit the
sawing of
wood with numerous knots and results in a surface ready for gluing. The ultra-
thin sawing
technique is more flexible (multiple saws) and economical than slicing (Figure
1 - Item 7
and Figure 3).
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CA 02434248 2003-07-03
6. Final drying of the thin boards in a high temperature press to stabilize
the thin boards. This
technique utilizes temperatures in excess of 100°C and includes cycles
of pressure
application, release and cooling. The Kock U.S. patent No: 3,689,219 describes
tis process
in detail. This pressing operation results in stabilized thin boards free of
defects and
splitting all the while conserving the structural characteristics in the thin
boards.
7. Sorting and ripping (Figure 1 - Item 9). Removal !butting of the thin
boards sections with
defects (Figure 1 - Item 9). These thin board sections will then be ripped to
eliminate
defects and redirected to production. The process thus utilizes a high quality
value added
clear of defects thin boards in the totality of the raw material utilized.
8. Assembly (Figure I - Item 11 ), pre-heating of the thin boards, glue
application, lateral
pressing and light calibration of the core with a trim saw calibration (Figure
I - Item 10
and Figure 7). This method enables the recovery of butt sawn lengths produced
in the
process.
9. Glue application on the faces and sides of the thin boards of the core
(Figure I - Item 11 )
and Figure 9), two dimensional pressing and final thickness calibration
utilizing sanding
equipment (Figure 1 - Item II and Figure 10 & 11). The glue is a structural
high
temperature type for construction applications, or PVA for other types of
application.
10. Cutting of the panel to customer specification and edge profiling (edge
band and ripping).
Other favorable aspects of balsam fir:
~ In the current lumber markets, the presence of water pockets in balsam fir
presents a
major problem due to the difficulty in their elimination.
~ The thin sawing of the wood into thin boards facilitates moisture content
uniformity in
balsam fir by way of the processing of these thin boards which permits the
possible use
of a high temperature press which would enable the integration of the drying
cycle in a
continuous production process.
CA 02434248 2003-07-03
The reference patents relating to solid wood paneling and laminated wood
products are the
following:
US patents:
US 3,680,219 (1972, Kock), US 3,875,685 (1975, Kock), US 4,402,781 (1983,
Couture et al.);
4,413,459 (1983, Lambuth), US 4,844,763 (1989, Robbins); US 5,002,106 (1991,
Binder), US
5,113,632 (1992, Hanson); US 5,234,747 (1993, Walser et al.); US 5,352,317
{1994, Traben et
al.); US 5,500,070 (1996, Traben et al.); US 5,648,138 (1997, Tringley), US
5,662,760 (1997,
Tsuda); US 5,747,151 (1996, Tringley et al.); US 5,725,929 (1998, Cooke et
al.), US 5,881,786
(1999, Wilderman et al.); US 5,888,620 (1999, Grenier), US 5,948,188 (1999,
Gibson); US
5,968,625 (1999, Hudson); US 6,001,452 (1999, Basset et al.); US 6,007,659
(1999, Hasegawa);
US 6,025,053 (2000, Grenier), US 5,507,905 (1996, Kairi); US 6,033,754 (2000,
Cooke);
US 6,174,483 (2001, Brown); 6,217,976 B1 (2001, Macpherson et al.);
Foreign patents:
CA 2,238,491 (1999, Grenier), EP 0841 135 A3 (1999, Kallesoe); EP 0 521 363 B1
(1992,
Traben); WO 99126768 (1999, Ohlson); WO 87102616 (1987, Le Bell et al.); WO
99122918
(1999, Gibson et al.).
