CA2434248A1 - Multi-ply solid wood panel from balsam fir - Google Patents

Abstract

The following constitutes a direct application of this value added process with respect to bailsam fir or other wood species with lighter weight characteristics. This application brings forth the inherent qualities of balsam fir which are lighter weight and dimensional stability contributing thus to the desired characteristics in integrated construction components of large dimensions:
therefore, production of these construction components lend themselves well to integrated construction methods such as sub-flooring systems.

Description

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Icle~lle e~'ej 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.
1 of 12 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 2of12 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.

3 of 12 ~ 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).
4of12 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.

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

(1999, Gibson et al.).

Claims (3)

1. The choice of light weight wood species of the SPFL group for structural and appearance applications thus obtaining adequate structural results all the while reducing the total flooring system mass as well as providing an appealing appearance of the product. The sub-claims are:
~ The choice of wood species with a density of less than 0.42 gr/cm3.

~ Structural specifications (MOE, MOR & SHEAR) for the lightweight woods and certification possibilities. Comparative results measured in Forintek Canada Corp.~
are presented in the following tables:

Stiffness Panel type & thickness Comparative stiffness .cndot. Solid Balsam Fir 5/4" (Guylam) 1,00 .cndot. OSB Grade "A" 3/4" 0,62 .cndot. OSB Grade a 7/8" 1,03 .cndot. Douglas fir plywood 5 ply 3/4" 0,85 .cndot. Douglas fir plywood 5 ply 7/8" 0,89 .cndot. Spruce plywood 5 ply 3/4" 0,58 .cndot. Spruce plywood 5 ply 7/8" 0,86 Baseline stiffness of 5/4" Solid Balsam Fir = 1.00 Weight Panel type & thickness Density Comparative (lbs/cu.ft.) weight/sq.ft.

.cndot. Solid Balsam Fir 5/4" (Guylam) 24,5 1,00 .cndot. OSB Grade A 7/8" 46,8 1,34

2. A modular panel concept for one layer sub-flooring differentiating itself by integrated characteristics and ease of installation, improved sound insulation, improved rigidity and lightweight. This claim has the following sub-claims:
~ The panel allows the installation with the panel ends in cantilever position with joists up to 24 inches of spacing.
~ An elongated narrow panel concept, up to 16 feet and more, improving the surface of the sub-flooring due to better surface homogeneity and structural integration with the joists.
~ Tongue and groove designed in relation to panel thickness, concentrated in the core layer.
~ Sound insulation characteristics as laboratory measured.

3. A manufacturing process which consist of stabilizing moisture content and dimensions by way of a high temperature pressing and drying operation in final phase: the sub-claims are:
~ A manufacturing process principle adapted to SPFL wood species and their properties.
~ A specific drying program utilizing high temperature pressing adapted to the wood species and configurations within the SPFL group of species having densities inferior to 0.42 gr/cm3.

structural products. The main offices are located in Vancouver and Quebec city.