Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
A structural wooden joist.
FIELD OF THE INVENTION
The present invention pertains to a structural wooden joist used in building
constructions.
BACKGROUND OF THE INVENTION
Wooden joists are used increasingly in a number of building applications. They
comprise top and bottom elongated chords with intervening struts joined to the
chords by means of scarfing.
One such wooden joist may be found described in U.S. Patent No. 5,664,393
issued to Applicant on September 9, 1997 and consists of lower and upper
chords which are joined by an openwork web structure. This web structure
includes, between opposite ends thereof, a series of horizontally-spaced
trapezoidal laminated panels defining of series of triangular spacing
therebetween. Each panel has opposite short and long sides adhesively joined
to the lower and upper chords respectively, and each panel is formed of short
obliquely extending planks adhesively secured edgewise to one another.
It has been found that such structure does not offer adequate resistance to
humidity variations which cause some deformation of the joist structure.
OBJECTS AND STATEMENT OF THE INVENTION
It is an object of the present invention to provide an improved wooden joist
which
overcomes the above-mentioned problem known in the prior art. The joist is
characterized by an openwork web structure joined to the chords wherein the
web structure consists of a series of connector members formed of inclined
branches, each branch being formed of at least two adhesively secured planks.
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The present invention therefore relates to a structural wooden joist which
comprises:
a) an elongated lower chord;
b) an elongated upper chord in a spaced apart generally parallel opposed
relation to the lower chord; and
c) an openwork web structure joining the chords; this web structure
comprising a series of connector members formed of inclined branches and
adhesively secured to the lower and upper chords; each branch of the connector
members being formed of at least two planks having contiguous sides
adhesively joined to one another; the connector members defining a series of
triangular openings in the web structure.
In one form of the invention, each opposite end of the web structure includes
a
laminated panel which is formed of a series of planks secured edgewise to one
another and having their upper and lower sides adhesively joined to the upper
and lower chords.
In another form of the invention, the obliqueness of the branches of the
connector members has a different angle relative to the horizontal plane of
the
chords depending on the height of the joist.
Other objects and further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter. It should be
understood, however, that this detailed description while indicating preferred
embodiments of the invention, is given by way of illustration only since
various
changes and modifications within the spirit and scope of the invention will be
come apparent to those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an elevational view of a wooden joist made in accordance with the
present invention;
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Figure 2 shows a V-shaped arrangement of two connector members;
Figure 3 is an end view of the arrangement shown in figure 2;
Figure 4 is an elevational view of one end section of the panel structure
joined
to a connector member;
Figure 5 is an elevational view of another embodiment of a wooden joist made
in accordance with the present invention; and
Figure 6 is another embodiment of a V-shaped arrangement of two connector
members.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to figure 1, there is shown a structural wooden joist, generally
denoted
10, which comprises an elongated lower chord 12 and an elongated upper chord
14 spaced apart generally in opposed relation to the lower chord.
An openwork web structure is displayed between the chords 12 and 14. In a
major portion of the web structure, there is shown two arrangements of
connector members 16, which extend diagonally between the upper and lower
chords 12 and 14. These obliquely extending connector members 16 define a
series of triangular-shaped openings 18 allowing for passage of various
building
utilities, such as electrical wires, water conduits, air ducts and like.
Referring to figures 2 and 3, there is shown a V-shaped arrangement of two
contiguous connector members 16a, 16b, each consisting of a pair of planks 24,
26 (for connector 16a) and 28, 30 (for connector 16b). Planks 24 and 26 are
secured to one another along their contiguous side 32, while planks 28 and 30
are secured to one another along their contiguous side 34. The planks are
preferably glued together. The opposite ends of the planks 24, 26, 28 and 30
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are scarfed. The scarf joints 24a, 26a, 28a and 30a are adhesively secured to
the upper chord 14 while the lower extremities 26b and 30b of the planks are
also scarfed and adhesively secured to the lower chord 12.
At each opposite end of the joist, the web structure includes laminated panels
36 and 38. Referring to figure 4, the laminated panel 38 is formed of a series
of
vertically extending planks 40 which are secured to one another in edgewise
manner, the planks having scarfed joints 40a and 40b, which are adhesively
connected to the upper and lower chords. The innermost plank 40' of the
laminated panel is joined to a connector member 16 by means of a scarfed edge
41 joined to the scarfed edge 43 of plank 28. A structural glue may also be
used
to further secure the panels to the chords.
Referring to figures 5 and 6, there is shown another embodiment 110 of the
present invention wherein the connector members 116 are adhesively secured
to the lower chord 112 and upper chord 114. In this joint, the web structure
has
no central region free of connectors such as shown in figure 1, the connector
members defining a continuous inclined branch arrangement between the two
end panels 136 and 138. As illustrated in figure 6, each connector member
116a, 116b is formed of two obliquely extending planks 124, 126 and 128, 130
having different width. These planks are joined to one another along their
contiguous sides 132, 134 as well as to the upper/lower chords in manner
similar
to that described above with respect to the connector member 16 illustrated in
figure 2.
The inclination given to the connector member 16 of figures 1-4 and 116 of
figures 5 and 6 depends on the height of the joist. For example, for the joist
shown in figures 1-4, having a height H1 of about 9.25 inches, for example,
the
angle a between the planks and the chord is about 35°. On the other
hand, for
the joist of figures 5 and 6 having a height H2 of about 11.25 inches, for
example, the angle a is about 42°.
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The wood used for all planks of the panel is a kiln dry wood, preferably one
selected from the group consisting of fir, spruce and pine. The wood fibers
extend in the longitudinal direction of the planks.
Also, the structural glue used in securing the planks together as well as used
in
the scarfing, is one preferably having a base of resin resorcinol such as
phenol-
resorcinol resin, or one having a base of urethane, or any one approved for
structural wood construction.
Although the invention has been described above in respect to specific forms,
it will be evident to a person skilled in the art that it may be modified and
refined
in various ways. For example, although a pair of planks has been illustrated
for
each branch, the latter could also be formed of more than two planks.
Additionally, a single plank could be formed of two superposed planks joined
by
finger joints and glue. It is therefore wished to have it understood that the
present invention should not be limited in scope except by the terms of the
following claims.
