Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: METAL FLOOR JOIST
FIELD OF THE INVENTION
The present invention is directed to a metal floor
joist and in particular a metal floor joist having an
integral reinforced end.
BACKGROUND OF THE INVENTION
The framing of floors for residential and commercial
construction has traditionally been accomplished using
suitably dimensioned wood members. While the use of wood
members makes the construction relatively simple, the use
of wood members has its shortcomings. The supply of
lumber is getting scarcer and costs have increased during
recent years. In addition wood can warp and go out of
shape when it becomes wet as well as being susceptible to
attack by vermin of various kinds including termites.
In recent years floors framed with sheet metal
joists have been employed. The use of sheet metal joists
provides advantages of dimensional stability, ease of
manufacture and conservation of natural resources among
others. However the use of sheet metal joists has not
gained widespread acceptance for various reasons. One
such reason is that the ends of the joists where they are
attached to a vertical wall require that they be securely
attached to the rim joist and that they be provided with
some reinforcement to provide the joist with the
capability of supporting the load at the ends. In the
past this has commonly been accomplished by using an L
shaped bracket of a height about equal to the web of the
joist. One leg of the bracket is attached to the web at
the end of the joist and the other leg is attached to the
web of the rim joist. Another solution employs a section
of steel stud or track equal in height to the height of
the joist web. The web of the stud or track section is
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attached to the web of the joist and one flange of the
stud is attached to the web of the rim joist. A
variation on this is shown in U.S. Patent No. 5,625,995
issued May 6, 1997 to Byron Martin. This patent
describes a special bracket shaped like a stud section
for attaching this joist to the header. While these
solutions provide the required attachment and reinforcing
for the floor joist, they significantly increase the
labor time required to install the steel joist system.
Consequently steel joist systems have not gained
widespread acceptance among the framing trades.
A modified ledger or rim joist has recently been
described in U.S. Patent No. 5,956,916 issued September
18, 1999 assigned to Steel Floor Ltd. in an attempt to
overcome the above problems. The web of the ledger is
provided with struck out tabs which extend
perpendicularly inwardly of the web at a regular spacing,
typically 16 inches on center. The tabs act as a
locating means and attachment means for the floor joist
as well as reinforcing the end of the web of the floor
joist. While the modified ledger joist makes the
attachment of the floor joist easier, it also introduces
new problems. The alignment of the ledger must be
closely controlled so that the floor joists spanning the
space between the ledge will. be properly aligned with the
struck out tabs. This will require additional labor time
by the framing trades. Additionally, as the location of
the tabs are fixed at the time of manufacturing of the
ledger, the flexibility in the spacing of the floor
joists is limited. In some cases such as to avoid a
service stack or to provide additional support below
partition walls, it may be necessary to adjust the
spacing of the floor joist or to install additional
joists. In addition if the load characteristics change,
the joist spacing required to support the load may
change. Another situation where the floor joists will
not properly align with the tabs is if the floor joist
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meets the ledger joist at other than right angles, e.g.
45 degree angles commonly encountered in bay window bump
outs. In those cases, another means for providing the
attachment and reinforcing of the end of the joist would
be required such as the bracket or stud section described
above, thus defeating the advantages of the modified rim
joist.
There thus still remains a need for an easy to
install means of attaching a steel floor joist to a rim
joist and reinforcing the end of the floor joist.
SUMMARY OF THE INVENTION
The present invention is directed to a floor joist
for use in a steel framed flooring structure. The floor
joist has a U-shaped rectangular cross section with two
parallel spaced apart flanges and a central web bridging
the flanges and connected to one edge of each of the
flanges. The central web has an extension on each end
thereof, the extension extending beyond the flanges a
distance of at least half the width of the flange.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention are
illustrated in the attached drawings of which:
Figure 1 is a perspective view of a floor joist of
the present invention;
Figure 2 is a perspective view of the end of the
floor joist of Figure 1; and
Figure 3 is a perspective view of a floor
constructed using the floor joist of figure 1;
Figure 4 is a perspective view of two floor joists
of Figure 1 meeting over a beam; and
Figure 5 is a perspective view of a second floor
constructed using the floor joist of figure 1.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A first preferred embodiment of a floor joist
according to the present invention is illustrated in the
attached figures generally indicated by the numeral 10.
The floor joist 10 has a generally C shaped cross
section with a web 12 spanning two parallel flanges 14 at
opposite edges of the web 12. The opposite edge of the
to flanges 14 have an inwardly turned extension to
strengthen the flanges when under load. The central web
12 is provided with extensions 16 on each end, the
extension 16 having a height slightly less than the
height of the web 12. The extension 16 extends beyond
i5 the end of the flange 14 a distance of at least half the
width of the flange 14. Preferably the extension 16
extends beyond the end of the flange 14 a distance of
about the width of the flange 14. When the joist is
manufactured, the extensions 16 lie in the plane of the
20 web 12 this allowing the joist to be easily stacked for
transportation. In order to make the bending of the
extension 16 easier, slots 18 are provided along the
desired bend line 20 between the web 12 and the extension
16. The provision of the slots 18 also forces the
25 extension 16 to be bent along this line.
In the construction of a floor, the rim or header
joists 30 are attached to the wall, generally by being
attached to the top plate 40 of the wall or being directly
30 attached to the vertical surface of the wall as is common
in balloon framing and with walls formed from insulated
concrete forms. The extensions 16 of the floor joists 10
are bent, generally perpendicular to the web 12. The end
of the joist 10 is placed in the opening of the rim joist
35 30, butting the extension 16 against the web 32 of the rim
joist 10. The extension 16 is then screwed to the web 32
of the rim joist 30 by suitable screws 36 and the
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flange 14 of the floor joist 10 secured to the flange 34
of the rim joist 30 by screw 36.
As illustrated in Figure 4, when two floor joists 10
meet over a beam 51, the extensions 16 reinforce the ends
of the joists 10. In those situations, the webs 12 of
the joists are attached to one another with suitable
fasteners such as screws 36 or bolts. The flange 14 of
the floor joists 10 are secured to the beam 51 by
suitable fasteners such as screws 36.
As illustrated in Figure 6, the floor joists 10 of
the present invention are of particular use where the
joists 10 connect to the rim joist or header at other
than right angles. In these circumstances, the extension
16 of the floor joist 10 is bent at an angle to match the
angle between the floor joist 10 and rim joist 30. In
this way, the extension 16 butts against the web 32 of
the rim joist 30 and is easily secured to the web 34 of
the rim joist 30.
The floor joist of the present invention is
manufactured using typical machinery such as roll formers
to bend the flanges from a suitable sized blank of metal.
The extension and slots may be formed by a cutting
machine either before or after the roll forming
operation. Once produced the joists are easily stackable
one within another in the typical manner as there are no
protrusions beyond the usual C shaped cross section.
The dimensions of the floor joists of the present
invention are those typically used in metal forming. The
floor joists typically have a depth of 8 to 14 inches,
more preferably 8, 10 or 12 inches and the flanges are
typically 11/2 to 2 inches wide. The joist are typically
formed of 14 to 20 gauge steel, most preferably 16 or 18
gauge.
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As illustrated in Figure 3, the provision of the
reinforced end is also of use in the construction of
bridging members 50 which are used to interconnect two
joists 10 intermediate their ends. The bridging member
50 is provided with the extensions 52 on either end which
are bent over to allow the bridging member 50 to be
attached to the webs 12 of the joists 10 by screwing
through the extensions 52 and into the web 12 of the
joist 10. The length of the bridging member is the same
as the spacing between the joists 10, typically 16
inches, although other lengths are possible depending
upon the design of the floor. In order to allow the
bridging member 50 to fit between the inwardly turned
extensions of the flanges 14, the height of the bridging
member is selected to be equal to or less than the
spacing between the inwardly turned extensions.
Typically for 8 and 10 inch joists, the height of the
bridging member will be 6 inches. This allows the
bridging member to fit in the space and be formed using
the machinery generally used for 6 inch steel framing
members.
The extensions may also be used to reinforce the
ends of lintels formed by attaching two joists of the
required length together back to back, each of the joists
having the extensions on both ends.
If desired to increase the web stiffness adjacent
the ends of the joists, the web in that region may be
embossed.
The floor joist of the present invention provides
for numerous advantages over those of the prior art. The
securement of the floor joist to the rim joist does not
require the use of additional support members such as
brackets or short sections of metal studs, thus resulting
in significant labour savings. Similarly, the connection
of two floor joists to one another over a beam does not
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require additional support members, also resulting in
labour savings. The floor joists of the present
invention are also easily adaptable to situations where
the floor joists meet the rim joist or header at other
than right angles.
Although various preferred embodiments of the
present invention have been described herein in detail,
it will be appreciated by those skilled in the art, that
variations may be made thereto without departing from the
spirit of the invention or the scope of the appended
claims.
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