Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: Fabricated wooden beam with multiple web members
TECHNICAL FIELD
This invention relates generally to lumber utilised in construction and
to derivatives of the forestry industry. It also relates to more specific
5 construction elements such as joists, girders, rafters and trusses.
PRIOR ART
The traditional wood beam was made in one piece cut from large trees
in appropriate size and length. That required a population of large trees
in which the lumber would be cut, and the quality and strength would
10 largely vary in fonction of the quality of the trees.
Through the years longer and stronger beams have been required and the
available trees have decreased in population and size. The costs of sawn
lumber has raised and high quality wood required for large beams has
become scarce. Many solutions have been brought up over the years to
15 make beams with smaller trees or other less expensive and more
available wood products keeping in mind the need for higher
requirements on the market. Fabricated beams allow for a more
efficient design in the utilisation of raw materials for a given strength
beam. It saves wood, reduces transportation cost and facilitates the
20 erection of wooden structures.
In construction, joists, rafters, girders and trusses generally support
loads applied in one direction, thus allowing for a fabricated beam
design that would support compressive and tension loads generated in
its chord members by such a load. It is seen that two or more joists
25 would be installed side by side to give stronger support to a structure at
a given point. It is then more desirable to have a rectangular section
shaped beam, to keep the proximity of the two beams to a minimum and
facilitate their binding to one an other. The present invention relates to
both principles of compression-tension in the chord members and while
30 providing a rectangular section for ease of installation side by side.
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Wooden beams and wooden I-beams of this general type are disclosed
more extensively in the following patents:
US 4,967,534 Lines, 1990 Nov. 06, Chord members are rectangular and
horizontal, with a single groove made in larger side of the rectangular
5 section; a web is provided with a necked down end to be matched by a
matching design in the groove. The web may be made of stratified
wood .
US 4,195,462 Keller, 1980 April 01, A web may be made of glued
particles of wood and having four shaped ends interlocking in a chord.
lO US 4.241.133 Lund, 1980 Dec. 23, A composite wood material is used
to form I beams with flakes having a grain direction parallel to a
longitudinal axis with length to width ratio of 4:1 to lO:l.
CA 1,067,272 Casselbrant, 1979, Dec. 04, Illustrates a beam made
according to a glued wood chip fabricating method.
15 CA 1,279,972 Lines, 1991, Feb. 12, Refers to the same system as US
4,967,534 above.
These patents are listed as exemples only.
More should be said on the effect of weather on some types of wooden
materials for example: solid webs may be made of wood chips, which
20 are cheap but not suitable for situations where no protection against
weather exists. I am mainly concerned with materials utilised in
construction and having some protection against direct weather effects.
A high degree of shape stability had to be attained, such as for the
acceptance of a pinpoint load at any position along a beam, The
25 generally high cost of manufacturing had to be lowered.
Improvements came with the arrival of a several wood layer web into
which adjacent layer fibres are perpendicular in direction and the web
is connected over its entire length by a tongued connection into a chord
member made of whole timber. The arrival on the market of particulate
30 pannels has been beneficial to the industry and a common method of
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jointing comprises a tongue particulate web into a chord. Other
attempts were made to improve the idea, such as wooden webs made of
oriented fibres connected to a high quality wood chord member, making
the product more expensive but not necessarily more technically
5 advanced. With today's technologies it has been possible to put together
a structural beam that will have good shape stability and higher bending
resistance. It is desired in the following lines to describe a new type of
fabricated beam structure that improves the stability and strength and
that can be manufactured at low cost.
10 OBJECTS OF TIIE INVENTION
It is a primary object of the present invention to provide a fabricated
wooden beam with the properties and advantages of a fabricated wooden
I beam but with similar dimensions as a standard lumber beam utilised
for joist, girder, rafter and truss, thus not requiring any different
15 assembly technique and/or dimensioning requirement.
One of the principal objects of the present invention is to provide a
wooden fabricated beam constructed from smaller lumber and other
derivative wood products such as Oriented Strand Board (OSB) and
Laminated Veneer Lumber (LVL) allowing for simplicity of fabricated
20 wooden beam structure and low manufacturing cost.
It is another object of the present invention to provide a joint between
web members and chord members which permits use of a standard
adhesive accepted by the different regulating agencies.
It is another object of the present invention to provide a better load
25 transfer from an upper chord member to a lower chord member through
a multiple web design assembly, thus reducing any loss of strength
caused by the elasticity of web member fibres.
It is another object of the present invention to provide a fabricated
wooden beam which may be produced in a continuous or non-continuous
30 assembly process and maintain high strength consistency.
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It is still another object of the present invention to provide a wooden
beam manufactured as joists, which may be utilised in diverse design
configurations to complete a wide variety of structural applications.
SUMMARY OF THE INVENTION
5 In the present invention the fabricated wooden beam is made of two
chord members and two web members, the chord members being made
of solid wood or Laminated Veneer Lumber (LVL) and the web members
from Oriented Strand Board (OSB), Waferboard or Veneer. The upper
and lower chord members and the two planar web members are all
10 interconnected by means of mechanical and adhesive secured joints.
The overall shape of the assembly is similar to standard wood boards on
the market allowing for easy assembly with existing apparels and
equipments on the market. Chord members are finger jointed to permit
production of indefinite lengths. Chord member are also provided with
15 two longitudinally extending grooves, one on each side near the edge of
the chord. Both web members have their edges shaped as to
substantially fit in the chord members' grooves. The final assembly has
a generally rectangular outside section matching the dimensions of
standard lumber or any other dimensions.
20 The present invention will be better understood and additional
advantages will become apparent from the following detailed
description.
DESCRIPTION OF THE INVENTION
The invention is explained in the following text in reference to a
25 preferred embodiment which is shown here, in the accompanying
drawings .
DRAWINGS:
FIG. lA Shows a preferred embodiment in cross section before
j ointing.
30 FIG.lB Shows the embodiment of FIG.lA after jointing.
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FIG.2A Shows the area of arrow 2 of FIG.lB.
FIG 2B Shows an alternative to FIG.2A.
FIG 2C Shows an alternative to FIG.2B.
FIG.2D Shows an alternative to FIG.2C.
5 FIG 2E Shows an alternative to FIG 2D.
DETAILED DESCRIPTION
Referring to the preferred embodiment drawings there is shown in
FIG l A or l B a wooden beam 20, fabricated from a pair of chord
members namely an upper chord 22 and a lower chord 24 and a pair of
l0 web members 26; the chord members 22 and 24 may be made of solid
wood or Laminated Veneer Lumber (LVL) and web members 26 made of
Oriented Strand Board (OSB), Waferboard or Veneer. The upper chord
member 22 has a longitudinal groove 54 in each corner of an interior
face 32, and a chord member centre tenon 51. A web member 26 has a
l5 longitudinal recess 50 in both its edges leaving a tongue 46 and a
mating end 48, to match the chord member groove 54 and the chord
member centre tenon 51.
As shown in FIG.lA or lB each chord member contains two longitudinal
groove sites 70 having one entrance portion to chord member groove 54
20 and one shoulder portion 68. The web members 26 have a tongue 46
thickness equal to the chord member grooves 54 width, and a web
shoulder 50 width slightly smaller than the chord member shoulder
portion 68 width to allow for some expansion of the web material
towards the outside of the wooden beam. Strict tolerances on web
25 tongue 46 thickness and chord member groove 54 width act as a self-
locking type joint when the web tongue 46 is forced into the chord
member groove 54. To complete the joint between the web members 26
and the chord members 22 and 24 all the surface in contact between
these members are coated with a suitable adhesive 64 before being
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forced into each other and held until the adhesive 64 has sufficiently
cured in place.
As shown in FIG.2 many types of web tongues 46 or chord member
groove 54 fit shapes could be utilised to achieve web member 26 to
S chord member 22 and 24 jointing, as long as the type of joint would
give good transfer of force for bending stiffness and moment capacity
and help maintain the web members 26 into the chord members 22 and
24 during an adhesive curing period when required in the process. It is
important to note that the thickness of the web member tongue 46 is
10 variable from 3/16" to 7/16" for construction applications, that is many
times the thickness of the flakes making the OSB, thus allowing for
sufficient strength in the joint when OSB is utilised.
Chord members 22 and 24 are finger jointed when their length is
insufficient to cover the whole beam length. The wood and the adhesive
15 64, are heated to recommended temperature, then two finger joints are
forced into each other and kept under pressure until the adhesive 64 has
properly cured. The web members 26 are jointed with a different
process such as with a tongue end for meeting a groove end but their
faces and the adhesive 64 are not heated.
20 In general practice the assembly chord members are made of solid wood
lumber of a standard dimension and the assembly is put together to fit
the industry standard dimension or any other dimension as represented
by dimension line 65. The control of the industry standard dimension
line 65 is achieved by the control of web member shoulder 50
25 dimension and by the assembly of the web 26 to the chords 22 and 24.
Thus the present structural fabricated beam may substitute for a solid
wood dimension lumber without making any changes or adjustments in
the dimensions called for on the construction plans, in thickness, width
and length. The web members 26 are generally made of Oriented Strand
30 Board (OSB), Waferboard or Veneer. The chord members 22 and 24 are
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generally made of solid wood or Laminated Veneer Lumber (LVL).
Chord members comprise an upper chord 22 which when working,
operates in compression, and a lower chord 24 which normally operates
in tension. It is not essential that the two chord members be identical in
5 height, but they are generally so to permit utilisation in reverse, the
upper chord being the lower chord and vice versa.
ADVANTAGE S
The double web members 26 (or multiple webs) design provide for a
better shape stability, a better load resistance and a better torsion
10 resistance, than a similar size standard lumber. The double web
members 26, or a multiple web design, provide for a better shear
resistance, a better bending resistance and a better stiffness resistance
than a single web member. The transfer of load forces is more uniform
between the two chord members, by having the webs parallel and
15 towards the outside of the fabricated beam. They transfer any reaction
force more uniformly into the chord members fibres ensuring a better
utilisation of all the fiber of the chord members section area, thus
diminishing any loss of compression or tension trough wood elasticity.
Some secondary advantages are similar stocking volume as for standard
20 lumber beam and better fire retardant than one web design.
The present invention is environmentally efficient by using smaller
trees and wood industry by-products, technically efficient by providing
a consistent high strength beam for load carrying capacity and
economically efficient by allowing for mass production thus lowering
25 manufacturing cost.
A test on a 2" x 12" double web beam of this present invention design
with solid wood chord members (2" x 4" MSR-Machine Stress Rated)
and OSB webs (5/8" thick) has given similar moment capacity and has
attained 70% of bending stiffness of a 3" x14" truss joint LVL/Plywood
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I-Joist beam, as per ASTM D 198 Standard flexure test. Actual double
webs are 3/8" thick each.
The chords are easy to transport. The webs are transported separately.
The webs may be different and vary from 2" to 24". The webs are
5 assembled only at the point of fabrication before use. There is no need
to use press fit, only glue. The webs may be made of various materials.
The central part may be insulated by ThermofoilTM or be lined by fire
retardant materials.
CONSTRUCTION OF A TYPICAL BEAM
10 A fabricated wooden beam has a generally rectangular outline section,
comprising a pair of chord members and a pair of planar web members
interconnecting the chord members by means of fitting adhesive secured
mechanical joints between chord members and opposed edges of the
parallel web members, the joints comprising two longitudinal grooves
15 in the chord members edges' corners, receiving adhesive and one edge
of a web member in each groove, the grooves having cross sections
shaped to provide a matching fit of the web members edge, providing
upon mating a substantially close fit to maintain a final cured assembly
high shape stability and force transfer between the two chord members
20 and helping adhesive properly cure without change in assembly
dimension therefor.
The chord members can be made of solid wood 36 or Laminated Veneer
34 Lumber (LVL) and web members from Oriented Strand Board 57
(OSB) or Waferboard 59 or Veneer 58, which may utilize a second
25 stratum 60, a third stratum 62 or more. The shape of the joints between
the chord members and the web members is such as is normally
acceptable in a manufacturing process according to the adhesive
utilised, in a continuous or non-continuous process, while maintaining
high consistency. The fabricated wooden beam may be used as joists,
30 rafters, trusses and girders, utilised in diverse design configurations, t~
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complete a wide variety of structural applications. The fabricated beam
may have more than two web members.
A general description entails a fabricated wooden beam 20 (FIG. l B)
with multiple web members comprising:
5 -an upper chord 22 -FIG. lA-, a lower chord 24 and two elongated web
members 26, the upper chord 22 being quadrangular and comprising an
exterior face 30, an interior face 32 and two parallel sides,
- a left web 40 comprising an external face 42 and an internal face 44, a
mating end 48 joining the internal face 44 to the external face 42, the
10 mating end 48 comprising a tongue 46, the left web 40 being left
handed and working in cooperation with a similar right web 41 being
right handed,
- the interior face 32 comprising a tenon 51 located centrally with
respect to the parallel sides and two opposed sites less prominent than
15 the tenon and each carrying a groove 54, the tenon 51 comprising an
extremity 52 and two opposed faces 56,
the internal face 44 at the mating end 48 being placed against the
opposed face 56 and the tongue 46 being in the groove 54 acting in
combination with adhesive means 64 causing the permanent joining of
20 the fabricated wooden beam 20.
Each groove 54 forms a rectangle located at or near one of the opposed
faces 56, the rectangle being suitable to receive the tongue 46. In
another version, the groove (FIG.2B) forms an acute angle 80. The
groove in FIG.2C forms a trapezium 84 with a far contact end 86 and
25 extending to a shoulder contact face 82 adapted to contact a web
shoulder 50. The groove in FIG.2D defines a short trapeze 92 having a
small end 90 acting as a far contact, the short trapeze 92 being
replicated by a mirror image trapeze leaving an angular recess 94 and
having a small end 98 near a side of the chord both short trapezes
30 protruding from the right web.
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The groove in FIG.2E comprises a half circle 88 with two shoulders, a
near shoulder 96 located near the tenon and an exterior shoulder 97 on
an opposite side of the half circle and coinciding with a side of the
chord, the half circle forming a wrapping for a protruding mating end of
S the web. The mating end may be provided with a recess adapted to
receive a stuffing material to fill the recess and the half circle to cause
intimate contact between the web and the chord.The orientation of the
grooves in FIG.2E and 2D may be inverted.
The embodiment of the invention herein illustrated presents a preferred
10 form and composition thereof and should not be construed as limiting.
The drawings described herein illustrate a very small sample of some of
the possible designs. From the above description it will be apparent that
there is thus provided a device of the character described which
possesses the particular features and advantages enumerated as
15 desirable, rendering the invention susceptible of modification in its
proportions, form, detail construction and arrangement of parts without
deviating from the principle involved, or sacrificing any of its
advantages, or modes of putting the invention into effect in any
assembly, and not limitative. Furthermore any failure to describe such
20 aspect is not intended to create any limitation to the present invention.
Any other aspects, advantages and modifications within the scope of the
invention will be apparent to those skilled in the art to which the
invention pertains. Thus the scope of the invention should be
determined by the appended claims and their legal equivalents, rather
25 than by the examples given.
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PARTS LIST
wooden beam 58 veneer
22 upper chord 59 Waferboard
24 lower chord 25 60 second stratum
26 web member 62 third stratum
exterior face 64 adhesive means
32 interior face 65 dimension line
34 laminated veneer 68 shoulder portion
36 solid wood 30 70 sites
left web 80 acute angle
41 right web 82 shoulder contact face
42 external face 84 trapezium
44 internal face 86 far contact end
46 tongue 35 88 half circle
48 mating end 90 small far end
web shoulder 92 short trapeze
51 tenon 94 angular recess
52 extremity 96 near shoulder
54 groove 40 97 exterior shoulder
56 opposed faces 98 small end
57 oriented strand board
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