Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
Method and system for glulam beams
FIELD OF THE INVENTION
[0001] The present invention relates to wood engineering. More
specifically, the present invention is concerned with a glulams fabrication
system and method.
BACKGROUND OF THE INVENTION
[0002] One the one hand, glued laminated timber, also called
laminated timber beams, glue-laminated beams or glulam, is a structural timber
product composed of several layers of dimensioned lumber glued together. By
laminating several smaller pieces of wood, a single large, strong, structural
member can be manufactured from smaller timbers, for use as ridge beams,
garage door headers and floor beams, vertical columns or horizontal beams,
often in curved, arching shapes for example. Glulam structural members thus
make use of smaller and less desirable dimensions of timber, yet are
engineered to be stronger than similarly sized members comprised of solid
wood. Glued laminated beams are used in a wide range of applications in both
commercial and residential construction.
[0003] On the other hand, solid dimensional lumber lengths typically
max out at lengths of 22' to 24', but may be made longer by the technique of
"finger-jointing" lumber by using small solid pieces, usually 18" to 24" long,
and
joining them together using finger-joints and glue to produce lengths that can
be up to 36' long in 2x6 size for example.
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[0004] There is still a need in the art for a method and a system for
fabricating glulam beams.
SUMMARY OF THE INVENTION
[0005] More specifically, there is provided a method for glulams
fabrication, comprising obtaining wood pieces of a target length from raw
materials; and assembling the wood pieces of the target length into structural
timbers of a target thickness; in a continuous line at a rate of up to 500-600
linear feet/minute, whereby moisture content, end joints, mixing and applying
of
adhesives, glue line pressure and clamping time are continuously controlled.
[0006] There is further provided a system for fabrication of glulams,
comprising a finger-jointing unit providing wood pieces of a target length;
and a
beam forming unit; wherein the wood pieces of the target length produced by
the finger-jointing unit are directly processed by the beam forming unit into
glulams.
[0007] Other objects, advantages and features of the present
invention will become more apparent upon reading of the following non-
restrictive description of embodiments thereof, given by way of example only
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] In the appended drawings:
[0009] Figure 1 is a flowchart of a system according to an
embodiment of an aspect of the present invention;
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[0010] Figure 2 is a schematical view of the system of Figure 1; and
[0011] Figure 3 is a flowchart of a method according to an
embodiment of another aspect of the present invention.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0012] A system 10 according to an embodiment of the present
invention will be described in relation to Figures 1 and 2.
[0013] The system 10 generally comprises a finger jointing unit and
a beam-forming unit 22.
[0014] A raw material reception station 14 is provided for reception
of raw materials, i.e. sawn, dried and graded wood pieces. A feeder 24 is used
to provide the wood pieces to the finger jointing unit, at a rate of about 180
lugs/minute and adjustable by a variable frequency drive (see Figure 2).
[0015] The finger-jointing unit includes a joint machining station 16, a
joint insertion station 18 and a sizing station 20.
[0016] The joint machining station 16 comprises a double shaper for
joint machining and glue application inside the joints. The glue is injected
using
a glue applicator, from an adhesive tank 27 (see Figure 2, for example). Up to
180 lugs may be processed by minute, at a rate adjustable by a variable
frequency drive, including dynamic braking.
[0017] An automatic transfer 30 transfers the wood pieces with their
glued joints from the double shaper 16 to the joint insertion station 18, at a
rate
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of up to 180 lugs/minute adjustable by a variable frequency drive.
[0018] The joint insertion station 18 comprises an assembly machine
26 for inserting the joints one by one, and a high capacity crowder 28 used to
apply pressure.
[0019] The sizing station 20 comprises a planer 32 and a flying saw
34. The planer 32 is for planning or surfacing the joint wood pieces by means
of
a rapidly revolving cutter, which chips off the rough surface in many
shavings.
The wood pieces are passed over or under the revolving cutter by power feed,
leaving a smooth or finished surface, thereby ensuring ensure clean and
parallel surfaces before gluing. The planer thus surfaces the wood pieces and
reduces them to a uniform thickness, at a rate between 100 and 600 feet per
minute. The flying saw 34 allows cutting the pieces of wood to predetermined
lengths from the continuously incoming joint-ended pieces of wood, at a rate
of
up to 400' (120 m) per minute.
[0020] The beam forming unit 22 comprises a conveyer feeder 36,
an adhesive distribution system 38 for application of adhesive on the surfaces
of the joint-ended pieces of wood, a stacking beam system 40 for assembling
the thus adhesive-covered joint-ended pieces of wood into a pre-determined
lay-up pattern, and an oven 46 for adhesive hardening. The oven 46 comprises
a conveyer oven entry 48, a lamination oven 50 using radio technology and a
hydraulic system for applying pressure, an exit conveyer 52, and a beam
recovery system and beam accumulation transfer means 54, as detailed in
Figure 2 for example.
[0021] It is to be noted that raw material consisting of laminations for
example, may be fed from a second raw material entry 14' (see Figure 1), and
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directly processed by the beam forming 22.
[0022] Then, a finishing station 42 typically comprises conveyers 56,
a precision end trim saw 58 for trimming, a planer 60 for commercial sizing of
the four faces, and an exit transfer 62
[0023] Tables 1 and 2 below give examples of raw materials used
and finished products (i. e. structural glue laminated beams) obtained,
respectively, for reference)
AFTER DRYING pieces /
SIZE Thickness Wi,dth package
1 X3 1,173 2,653 594
1X4 1,174 3,613 432
2X3 1,647 2,692 418
2X2 1,732 2,231 494
2X4 1,630 3,664 304
2X6 1,660 5,700 160
2X8 1,660 6,700 160
Table 1
roducts Dimensions
ength 8' to 52'
idth 1 3/4"to 7 1/2"
eight 3 1/2" to 30"
Table 2
[0024] Dust collecting units 60 are distributed along the line, so as to
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collect saw dust that would otherwise contaminate the system and be harmful
for the workers around.
[0025] A method 100 according to an embodiment of a further
aspect of the present invention generally comprises feeding sawn, dried and
graded wood pieces (110), obtaining wood pieces of a target length (step 200);
and assembling them to yield structural timbers of a target thickness (step
300),
in a continuous line.
[0026] Species of wood used have known structural capacity, such
as black spruce of a density of about 28.04 and jack pine of a density of
about
24.92 for example, which are resistant softwoods. The raw lumbers are sawn,
dried and graded. The moisture content of the pieces of wood is determined
with a meter that checks the moisture thereof prior to adhesive application on
the pieces of wood.
[0027] Generally, the moisture content of the wood pieces is to be
below 16% at the time of bonding, except when it is known that the equilibrium
moisture content of the final product in use is 16% or more. In such case, the
moisture content of the wood pieces at the time of bonding may be up to 20%.
Wood pieces with moisture content greater than the given threshold (such as
20% for example) are re-dried, through air-drying or kiln drying for example.
The average range of moisture content of the resulting finished beams shall
not
exceed 5 %.
[0028] Moisture content of a finished timber is based on the average
content of the cross section thereof whereas the moisture content of a wood
piece to be layered is based on the average moisture content along its length.
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[0029] In step 200, the sawn, dried and graded lumbers are finger-
jointed (end-jointed) together using finger-joints and glue to produce wood
pieces of a target length, which is the length of the finished glulam,
generally
greater than the length commonly available from as-sawn lumbers. The
lumbers are thus joined to produce longer lengths, which are then machined on
both ends with a shaper such as a cutter head. A structural resin is applied
and
the joints are mated. A polyurethane adhesive with a woodbonding resin, such
as a mix UX-100/WD3-A322 for example, may be used. The resin is cured with
the joint under pressure in an assembly machine 26 and crowder 28. The end-
jointed wood pieces are planed on both sides to yield boards with clean,
parallel surfaces for gluing. Once the end-jointed lumbers have been planed
into boards, flanges are cut by a flying saw to obtain desired lengths.
[0030] It is to be noted that there is no need for a drying step
between steps 200 and 300. Moreover, there is no need to perform continuous
traction tests on the end-jointed lumbers.
[0031] In step 300, a high quality permanent adhesive is spread onto
the end-joint boards with a glue extruder. A crosslinking agent such as CX-47
and woodbonding resin such as WD3-A322 for example are used. Table 3
below shows characteristics of adhesives and cross-linking agents that may be
used.
Adhesive Appearance Solids Viscosity Spindle Specific PH Flash Pounds Freeze
name (X) Brookfieid, Gravity at Point per thaw
cps 25 F gallon Stabilit
`.
WD3-A322 White, 53,5- 1000- 2000 N04@ 1,09 4,5- >200 9,1 Yes
Woodbonding opaque fluid 57,0 10 rpm. 6,0
adhesive 25 C=
resin 3000 -
6000
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CX-47 Cross White, 43,0- 4500 -6000 N 4@ 1,15- 6,0 >200 10 None
Linking agent opaque fluid 46,0 10 rpm. 1,25 -7,0
25 C
UX-100 Amber 100% - N 4@ 1,10 - - 460 9,3- -
Polyurethane Viscous Solvent 10 rpm. 1,20 10,0
polymer liquid free 25 C=
adhesive 3,000 -
6,000
Table 3
[0032] The end-joint boards, once thus resin coated, are clamped
together into a pre-determined lay-up pattern inside a stacking beam system by
a hydraulic system inside a radio frequency oven, so that the stacked boards
are submitted to heat and pressure. Pressure is to be maintained during a
period of time sufficient to ensure close contact between the boards while not
over-stressing glue-lines during the development of the bond strength. The
average cooking time may be comprised between 3 and 7 minutes per section
of 16 feet wood pieces, at a temperature between 149 and 194 F (i.e. between
65 and 90 C) and under a pressure comprised between 1100 and 1500 psi
(i.e. between 7584 and 10 342 kPa). After the resulting timbers are removed
from the oven by the hydraulic system, their wide faces (sides) may be planed
or sanded to remove beads of resin that may have squeezed out between the
boards. Their narrow faces (top and bottom) may be lightly planed or sanded
depending on appearance requirements. Their edges (corners) may be
squared (90 degrees). The specified appearance of the desired timbers
dictates whether additional finishing is required at this point. For example,
knotholes may be filled with putty patches and the timbers may be further
sanded. End sealers may be further applied to the timbers. Then, the finished
timbers are wrapped, attached and shipped.
[0033] There is therefore provided a continuous system and method
for producing glulams, at a rate of up to 500-600 linear feet/minute, in a
single
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line, wherein moisture content, end joints, mixing and applying of adhesives,
glue line pressure and clamping time are continuously controlled to turn low
value logs into high grade lumber, at a competitive cost.
[0034] An average time duration from the raw material to the glulams
is about 15 to 20 minutes since the jointed boards go directly to the stacking
and gluing step, whereas in the case of standards installations where jointing
and stacking are made in different lines, due to the need of transfer,
transient
storage and intermediate glue drying, the process may take about 12 hours.
Such a reduced time allows a tighter control of glue adhesion for example, and
yields an increased quality of the end products.
[0035] Since the glulams are made from smaller pieces of wood,
which can easily be bent, curved glulam beams may be fabricated.
[0036] The finished timbers are structural glue laminated beams
have increased strength capabilities compared with the starting products, and
meet high quality standards, in terms of shearing resistance, delamination
resistance, fire resistance, dimensional stability and traction properties.
[0037] Glulam of the present invention may be used in a range of
structures for architectural and structural purposes, including domestic
construction, recreational buildings, industrial strictures requiring large
column
free spaces, and other structural uses.
[0038] Although the present invention has been described
hereinabove by way of embodiments thereof, it may be modified, without
departing from the nature and teachings of the subject invention as defined in
the appended claims.
