Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIELD OF THE INVENTION
The present invention relates to waferboard
lumber, more particularly the present invention relates to
lumber products formed from wafers oriented to be substan-
tially parallel to the longitudinal axis of the lumber
product and a method of producing such product.
BACKGROUND TO THE PRESENT INVENTION
There have been many patents issued and many
papers published on the manufacture of lumber-like
products from wood particles. Similarly it is common
practice to manufacture waferboard-type panel products
from wood particles and there have been a number of
articles published.
In the realm of oriented strandboard, the normal
practice has been to manufacture a board from particles
having a maximum length of up to about 4 inches (100 mm)
and many papers and articles have been published advocat-
ing 4 inches (lO0 mm) as a maximum length of wafer.
Australian patent 136,844 issued March 28, 1950
is one of the earlier disclosures relating to the manufac-
ture of lumber from particles. In this patent the
particles recommended are sticks, twigs, etc that are
oriented in the longitudinal direction of the lumber and
secured together. It has also been proposed in
Czechoslovakian patent number 93,154 issued December 15,
1959 to Stofko, to produce a moulded product by orienting
wood elements in what are broadly defined as profiles such
as I, U, T, L and others including pipes and windows, and
pressing to consolidate into a finished or semifinished
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product. The teachings of this patent are further ampli-
fied by articles published by Stofko in Drevarsky Dyskum 2
No. 1:81-102 (1957); Drevarsky Dyskum 5 No 2:241-261
(1960), Drevarsky Dyskum 2:127-148 (1962) and Drvna
Industriaja 21 (6):104-107 (1970). In these articles
Stofko discusses panel products and lumber products
presumably moulded as -taught in his patent and emphasizes
the importance of slenderness ratio, i.e. the ratio of
length to thickness of the wood particles to obtain the
desired structural properties at an acceptable density.
United States patent 3,164,511 issued January 7,
1965 to Elmendorf discloses the manufacture of a lumber
product from wafers having length of up to about 6 inches
(150 mm), width up to about 1/4 inch (150 mm) and thick-
nesses between 0.005 to 0.02 inches (0.1 to 0.5 mm). To
applicant's knowledge no commercial lumber products
utilizing such wood particles have been manufactured and
sold.
U.S. patent 3,956,555 issued May 11, 1976 to
McKeen describes the manufacture of a laminted beam from a
comb;nation of or;ented and random wood particles in a
press by lay;ng alternative strips of oriented and random
particles and then consolidating under pressure to form a
panel and splitting the oriented strips to divide the
panel in to structures hav;ng end side sections that are
oriented and would function similar to flanges of an
beam interconnected by a random oriented section that
would function as the web of an I beam. This is a rela-
tively complicated structure with lim;ted strength and
suitable only for use with the products oriented to be
loaded perpendicular to the split faces.
As far as applicant is aware, the product
described in U.S. patent 4,061,819 issued December 6, 1977
to the present inventor describes the only commercially
v;able suitable lumber product formed from wood particles
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(strands). This patent teaches the use of relatively
long strands -to obtain structural products having physical
characteristics including density and strength character-
istics similar to, and in some cases better than, those of
the natural wood product it replaces.
United States pa-tent 4,122,236 issued October
24, 1978 -to Holman describes an artificial lumber product
moulded from splinters having a length in the range of
about 2 to 10 inches.
Generally when waferboards (panels) or the like
are made, the density proFile through the panel is such
tha-t the skins of the panel have maximum dens;ty and the
core has the least density. Stated another way, the
strength of the skins of the panel is higher than the
strength of core, however, since panels are normally used
with the core extending along the neutral axis of the
bend;ng moment such a density distribution is not a major
factor in determining bending strength. It is known that
the rate of pressure application in a press can be used to
change the density profile -through the thickness of the
panel. Also in a continuous pressing operation the rate
of temperature rise coordinated with the rate of pressure
app1ication can be used to change the density profile with
thickness to the panel.
It is economical to produce wafers since the
wafers are normally produced by a blade having spaced
edges equal in length to the length of the wafer to be
produced cutting substantially parallel to the grain.
In some cases flat blades cutting parallel to the grain
are used with spaced spurs cutting perpendicular to the
grain to define the length of the wafers. Wafers so
produced are generally relatively thin and have a width
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many times greater than their thickness (thickness being
determined by the depth of cut of the blade and the width
being determined by the deflection of the cut wafer by the
breaker bar of the knife).
BRIEF DESCRIPTION OF THE PRESENT INVENTION
It is an object of the present invention to
provide a lumber product formed utilizing waferboard tech-
nology and wafers having the following average geometry;length at least 8 inches (200 mm) maximum thickness of
0.15 inches (4 mm) and a width of at least 0.25 inches (6
mm) to provide a relatively inexpensive lumber product
having physical characteristics similar to or better than
those ob-tained from lumber made from the same species as
the wood flakes.
Broadly the present invention relates to a
waferboard lumber product and a method of making same,
said waferboard lumber product comprising discrete lengths
of lumber having thlcknesses of at least 1 inch (25 mm)
made from a single layer panel formed from wood wafers,
said wafers being oriented to have their lengths orien-
tated to the longitudinal length of the panel measured in
the major plane of said panel with a mean deviation of O
to 10 degrees and a mean deviation measured in a minor
long-itudinal plane through the panel perpendicular to the
said major plane of from O to 5 degrees, said wafers
having an average effective length of at least 8 inches
(200 mm) said lengths of lumber having cut edges defined
in said panel by cuts extending substantially longitu-
dinally of said panel said cuts being spaced defined the
width of said lumber.
Preferably said wafers will have a maximum
average thickness of 0.15 inches (4 mm) and an average
width of at least 0.25 inches (6 mm).
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Preferably said lumber product will have a
substantially uniform density to thickness profile.
Present invention also relates to a method of
making a lumber product comprising laying up a single
layer panel having a thickness of at least 1 inch (25 mm)
from a plurality of wafers, orienting the longitudinal
length of said wafers relative to the longitudinal axis
of said panel so that the mean deviation of the lengths
of said wafers to said longitudinal axis of said panel
measured in the major plane of said panel is in the range
of O to 10 degrees and a mean deviation measured in a
longitudinal plane through said panel perpendicular to
said major plane of from O to 5 degrees, said wafers
having an average effective length of at least 8 inches
(200 mm) consolidating said layup of wafers under heat and
pressure to set adhesive coating said wafers and consoli-
date said layup into said panel having a substantially
uniform density to width profile and cutting the panel
along spaced longitudinally extend-ing lines to divide said
panel into a plurality of discrete lumber lengths having a
width equal to the spacing between said longitudinal cuts.
Preferably the consolldatlng conditlons wlll be
controlled to yield a panel havlng a substantially uniform
denslty to thlckness profile.
Preferably the dens~ty of the lumber products so
produced wlll be ln the order of 25 lb/ft3 (0.4 g/cm3)
through 50 lb/ft3 (0.8 g/cm3). Also preferably the density
will not deviate more than 3% from the mean through the
panel thickness.
8RIEF DESCRIPTION OF THE DRAWINGS
Further features, objects and advantages will be
evident from the following detailed description of the
preferred embodiments the present invention taken in
conjunction with the encompanying drawings in which
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Figure 1 is a schematic plan view of a plan for
carrying out the present invention.
Figure 2 is a schematic side elevation of the
plan of Figure 1.
Figure 3 is a partial plan view of a board or
panel constructed in accordance with the present inven-
tion, illustrating the lay of wafers therein.
Figure 4 is a sectional view along the line 4-4
in Figure 3.
Figure 5 is a graph of density versus thickness
illustrating a preferred density profile with thickness
through the board of Figure 4.
Figure 6 is a sectional view along the line 6-6
in Figure 4.
DESCRIPTION OF PREFERRED EMBODIMENTS
The term wafer used throughout this disclosure
is intended to define wood particles formed by a waferizer
as distinct from pulp chips, sawdust, particles or lengths
cut directly from a round log or formed by clipping
veneer. The size of the sliced wafers used with the
present invention, particularly the length which is always
measured in the fiber direction, i.e. parallel to the
longitudinal axis of the fibers, is critical to obtaining
the required strength to provide a lumber product to
replace conventional lumber with a product having essen-
tially the same strength as the lumber being replaced and
without a significant change in density.
Referring to Figure 1, adhesive coated wood
wafers are brought to the layup forming equipment via a
suitable in-feed device wherein the wafers are relatively
uniformly laterally spread and are then fed to an orient-
ing device 12 (see for example U.S. Patent 4,494,969
issued January 22, 1985 to Knudson et al) that orients the
wafers with their longitudinal dimensions substantially
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aligned as will be described in more detail here below.
In the illustrated arrangement the mat 14 so Formed has a
substantially uniform density to width profile and is
either layed on a caul plate and transported to a press
such as a multiopening press schematically illustrated in
16 or is carried by a continuous belt or the like to a
continuous press 16 and the mat or layup 14 is pressed and
consolidated to form a panel 18, say a panel having a
total width of 8 feet (2400 mm) and the required thickness
(e.g. for nominal 2 inch (50 mm) lumber the consolidated
panel must have a 1-1/2 inch (38 mm) thickness). If a
continuous press 16 is used panel 18 is continuously moved
from the press 16 in the direction of arrow 20, i.e. in
the longitudinal direction of the wafers which is the
direction in which the wood fibers are aligned in the
wafer, into the cutting station 22. If the press 16 is
not a continuous press, i.e. is a multiopening press or
the like the mat 14 is carried on a caul plate to be
consolidated into a panel, the panel will be withdrawn as
indicated by arrow 20, separated from kheir respective
caul plates (not shown) and fed one following the okher in
the direction of the arrow 20, i.e. with the length of the
wafers aligned with the arrow 20 into cutting station 22.
Cutting station 22 as schematically illustrated
is made up of a purality of spaced circular saws or
cutters 24 axially moveably mounted via hubs 26 on a shaft
28. Hubs 26 are mounted in a conventional manner to be
driven by the shaft 28 and yet slidable axially on shaft
28 so that the position of the saws 24 may be adjusted
thereby adjust the width of the spaces between the saws
which determines the width as indicated by the dimensions
W1, W2, W3, etc of the lumber products 30 formed from
panel 18 (which may be any appropriate width). Figure 2
further provides a schematic illustration of an automatic
spacing device adapted to adjust spacing between saws 24
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including a yoke 32 that engages its respective hub 26 and
is moved along a shaft 34 by a suitable drive bar 36.
There will be one drive bar 36 for each yoke 32 and one
yoke 32 for each of the blades 24 to in known manner
adjust the position of the saw 24 along the shaft 28.
Generally the spacing of the saws or cutters 24, i.e.
widths W1, W2, etc, will be greater than the thickness T
of the panel.
The two outermost blades, i.e. the -top and
bottom blade 24 in Figure 1 are used to trim the panel 18
and provide trimmed strips as indicated at 38.
A suitable cut off saw schematically indicated
at 40 traverses the panel 18 after the appropriate length
of cut boards 30 has passed the saws 24 to cut the boards
off to the required lengths. In continuous operation the
saw 40 wlll move both transversely and longitudinally so
that a square cut is provided across the width the panel
18 (see the arrows 42 and 44 in Figure 1) and where
discrete panels 18 are formed on caul plates the cut off
saw may not be necessary but may be useful for trimming to
length.
It is intended -that press 16 be operated as
above indicated to provide a panel 18 of adequate strength
which requires that wafers having at least an average
length of about 8 inches (200 mm) (length is always
considered as measured in direction of the grain of the
wafer) preferrably an average length of 10 to 24 inches
(250-600 mm) be used. Normally such wafers will be cut at
an average thickness not exceeding 0.15 inches (4 mm),
preferably less than 0.1 inches (2.5 mm) with the thicker
wafers normally being used to produce the thicker panel.
The wafers will preferably have an average width of at
least 0.25 inches (6 mm), more preferably at least 0.5
inches (12 mm) and in many cases will have a width to
thickness ratio of over about 10.
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The wafers must be oriented with their length
direction aligned relative to the longitudinal direction
of the lumber which as above indicated is formed by
cutting subs-tantially parallel to the longitudinal direc-
tion of the panel 18 or parallel to -the direction of out-
feed from the press 16. This orientation will never be
100% in the machine direction, i.e. parallel to the
longitudinal axis of the panel 18 and the axial length of
the lumber products 30, but will be such that the mean
deviation of the wafer lengths (fiber direction) from the
longitudinal axis of the panel 18 and thus form the longi-
tudinal axis of the lumber product is within the range of
approximately 0 to 10 degrees when measured in the major
plane of the panel 18, i.e. measured on say the upper
surface of the panel 18 as indicated at 46 in Figures 2
and 3. The mean deviation measured in a plane extending
longitudinally to the panel 18 or boards 30 say parallel
to the cut faces formed by the saws 24 (i.e. perpendicular
to the plane 46) wlll normally be in the range of 0 to 5
degrees as schemat-ically illustrated by the angle A in
Figure 4. The angle A will preferably be small closer to
the 0 to 3 degrees since if the angle A is too large and
wafers extend almost from one major surface of the panel
to the other~ a weak product will be produced and this
must be avoided.
Press cycle wlll be controlled (including the
rate of change of temperature assuming a continuous press)
depending on the product to be produced but normally will
be such that the density to thickness profile is substan-
tially constant, i.e. a deviation of less than 3% from themean for a normal lumber product. Generally the faces of
the panel 18 contacting the press plates will have a
slightly higher density than the central portion of the
panels. If the lumber product is to be used as planking,
i.e. with the loading perpendicular to the major face, it
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may be desirable to manufacture a panel with distinct core
and surface layers with the surface layers having a signi-
ficantly higher density than in the core. With a plank
the deviation in density from the mean may be as high as
10% depending on the relative thickness of the dense
surface layers to the less dense core portion.
The uniform profile of density to thickness is
significantly more important with the structural lumber
product of the present invention which will normally be
loaded perpendicular to its cut or edge face, i.e.
parallel to the face represented by surface 46 of panel 18
so that the major faces of the panel which contact the
platens of the press will be aligned with the load and the
center or core of the panel no longer forms the neutral
axis when the structural member is being stressed.
In the operation of the present invention suit-
able wafers as above described are first formed in a mat
14 of approximately 4 times the desired finished thickness
of the panel 18 which will normally limit the maximum
thickness of the panel to about 4 inches (100 mm). The
wafers will be precoated with adhesive normally a phenol
formaldehyde resin although lsocyanates may also be used
or any other suitable adhesive. Normally if phenol for-
maldehyde is used a dried powdered resin will be used
25 although with proper application a wet or liquid resin may
also be used. Change in resin may require a change in the
pressing schedule to ensure proper curing of the resin
when the mat is under pressure.
Assuming the lumber to be produced is nominal 2
inch (50 mm) thick lumber then the thickness of the panel
18 will be 1-1/2 inch (40 mm) and the cutters 24 will be
separated to cut the panel 18 into strips and to produce a
2 x 6; 2 x 8; 2 x 10; 2 x 12; or even 2 x 16 inch; etc,
lumber as desired. Generally the wider the width dimension
the more valuable the product yet it is as easy to manu-
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facture a 2 x 16 inch board as it is to manufacture a 2 x
4 utilizing the present invention and any desired product
mix may be made. Furthermore, if a continuous press is
used the length of the boards so formed is determined sim-
ply by activation of the cutoff saw 40 to cut the boardsto the desired length. If caul plates are used the saw 40
may simply be used to trim the lumber to length or alter-
natively it could be trimmed at some other stage. In this
case the maximum length is determined by the length of the
caul plate.
EXAMPLE 1
A single layer oriented wafer mat was hand felt-
ed aspen wafers onto an 8 foot (2400 mm) long caul plate.
The wafers used were 12 inches long and 0.025 inches (0.6
mm) thick and 1-1/4 inch (30 mm) wide and were produced at
MacMillan Bloedel's Thunder Bay Division. 5% powder phenol
formaldehyde resin and 2% slack wax were applied to the
wafers. A matching 8 foot caul plate was placed on top of
the mat before pressing. The felted wafer mat was then
advanced through a hot press (in the Research Centre under
lab conditions) in 2 foot stages. Each stage was pressed
for 20 minutes at a press temperature of 210C. The
resulting product had a thickness of 1-1/2 inches and
an average density of 40 lb/ft3 (0.64 grams/cc). The
modulus of elasticity (MOE) of the section so produced was
1,697,000 psi (11.70 GPa) measured while applying forces
parallel to the faces formed by the caul plates, i.e. in a
direction equivalent to perpendicular to the cut faces of
the lumber product.
It will be apparent that the pressing of this
sample was not under ideal conditions so that the panel
produced was far from ideal. However the sample clearly
indicates that the modulus of elasticity (MOE) is at least
equivalent to that for conventional lumber of the grade
specified and at a reasonable density.
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EXAMPLE 2
In a further attempt to determine the applicabi-
lity of utilizing wafers that are relatively inexpensive,
a relatively thin aspen veneer 0.05 inch (1 mm) thick at
10% moisture content was clipped to 12 i nch length by 1/2
inch width strips to make an 8 foot long, 11 inch wide by
2-1/2 inch thick oriented lumber billet utilizing a
continuous press, microwave heating, 6% powdered phenol
formaldehyde resin and 2% slack wax. A mat was formed
from wafers precoated with adhesive and oriented to sub-
stantially align with the length of the lumber product and
passed through the press over a period of 9 minutes. The
actual specific gravity of the resultant lumber was 46
lb/ft3 (0.64 grams/cc) at 12% moisture and the resulting
board had an average MOE of 1,65Q,OpO psi and a modulus of
rupture (MOR) of 6900 psi.
Another board made in a similar manner had a
specific gravity of 39 lb/ft3 (0.54 g/cc), a MOE of
1,500,000 ps; and a MOR of 5,500 psi.
Examples 1 and 2 clearly demonstrate that it is
practical to manufacture lumber products having acceptable
physical characteristics for structural lumber applica-
tions when made from a species such as aspen which ls not
a good species for such materials and at a final density
that while higher than aspen is similar to that of many
species.
Having described the invention modifications
will be evident to those skilled in the art without
departing from the spirit of the invention as defined in
the appended claims.
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