Note: Descriptions are shown in the official language in which they were submitted.
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SUSPENDED JIG FOR ROOF CONSTRUCTION
Field of the Invention
The present invention relates to a method and apparatus for forming roof
truss assemblies du.~ing roof construction.
S Background of the Invention
A roof frame must be able to support not only the graviton load of the roof
itself, but also need to withstand additional loads due to construction; snow,
wind,
and earthquake. In most current construction the roof is supported by a roof
truss
framework. The use of roof trusses offer several advantages to a builder,
including
enhanced strength, greater economy (as trusses use both fewer and shorter
lengths
of lumber than alternative roof framing), and the availability of a variety of
different truss shapes and styles, including custom truss designs. In
addition, the
use of a roof truss frame permits greater
flexibility in the layout of the. building interior, as the truss frame
typically
transfers the entire roof load to the exterior walls.
However, the use of trusses in roof construction' presents disadvantages as
well. Although many types of trusses are commercially available and
preassembled, the trusses must still be raised to roof level and assembled
into the
roof frame. Truss assembly typically requires construction at well above
ground
level, and therefore brings with it the hazards and problems associated with
working at such a height. Even beyond the risks due to falling, framing and
sheathing a roof requires accuracy and precision, which can be made more
difficult to achieve when working at a significant height.
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It would be safer to assemble a desired roof frame at ground level and then
raise the entire assembly into the desired position. However, many job sites
lack
an appropriately sized and sufficiently level location to permit accurate
truss
framework assembly. The necessary leveling and alignment of truss members is
difficult to achieve at ground level as it ideally requires that each mass
should be
rendered plumb and level before incorporation into the truss framework.
Unfortunately errors in assembling the truss framework may not be discovered
until the completed framework is hoisted into position on top of the
supporting
walls_ Making the necessary repairs or corrections once- the truss assembly is
in
place at height is at least awkward, and may be dangerous.
Suanmary of the Invention
The invention provides a roof framing jig and a method of using the roof
framing jig to assemble a roof truss assembly. The roof framing jig includes a
jig
frame, a hoist connection for suspending the jig frame, and a plurality of
truss
supports secured to the jig frame, where each truss support is adapted to
suspend
an individual roof truss. The jig is configured to suspend a plurality of
individual
roof trusses in a predetermined spacing and orientation to facilitate
construction of
a truss assembly. The method aspect of the invention positions a roof framing
jig
that includes a jig frame, a hoist connection adapted for suspending the jig
frame,
and a plurality of truss supports secured to the jig frame. Each truss support
is
adapted to suspend an individual roof truss. -The next step is to suspend at
least two
individual roof trusses from at least two truss supports, with the jig being
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configured such that the individual roof trusses are suspended in a
predetermined
spacing and orientation. The roof trusses are then braced to form a truss
assembly.
Brief Description of the Drawings
Figure 1 is a schematic isometric view of a roof truss jig according to one
aspect of the present invention.
Figure 2 is a front view of a horizontal beam of the roof truss jig of Figure
1.
Figure 3 is a partial schematic isometric view of the roof truss jig of Figure
1, showing details of a truss support.
Figure 4 is a schematic view of a truss assembly suspended from the roof
truss jig of Figure 1.
Figure 5 is a schematic view showing a sheathed truss assembly being
hoisted into place on a building frame.
Detailed Description of the Preferred Embodiment
Fig. 1 shows a roof truss jig 10, constructed in accordance with an
illustrated aspect of the present invention. The roof truss jig IO includes a
jig
frame 12, a plurality of truss supports 14, and a hoist connection 16. Roof
truss jig
10 is configured so that when a preassembled roof truss 18 is suspended from
jig
frame 12; the roof truss can hang horizontally level and vertically plumb with
a
desired truss spacing. The roof trusses may be subsequently braced and/or
sheathed to form a truss assembly.
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Roof Truss Jig
Jig frame 12 may include one or more beams, which may be horizontal
beams, such as beams 20 and 21 as shown in 1~igure 1. The jig frame beams
serve
as attachment points for a plurality of truss supports 14. Generally, the
number of
truss supports that may be supported by a given beam is dependent upon the
length
of the beam and the desired spacing between trusses. Preferably, truss
supports 14
are adjustably supported by beams 20 arid 21, so that the spacing between
individual truss suppot-tts may be varied.
Horizontal beams 20 and 21 may be coupled to, and suspended from, beams
22 and 23 by one or more beam couplings 25. Beam couplings 25 may be fixed
couplings or adjustable couplings. Where the beam couplings are adjustable,
the
spacing between beams 20 and 21 may be altered to accommodate a variety of
truss sizes. Adjustable beam couplings may incorporate bolts that are inserted
into
predrilled holes or slots in beams 20 and 21, beams 22 and 23, or both. The
predrilled holes or slots, when present, typically correspond to one or more
preselected fixed spacings between beams 20 and 21. Typically, the preselected
spacings would be chosen so that the resulting configuration of the jig frame
is
symmetrical about the center of the frame, to increase stability and balanced
loading of the frame. Jig frame 12 may include adjustable beam couplings so
that
the roof truss jig of the invention may be partially dismantled to facilitate
transport
of the jig to a work site. Alternatively, beam couplings 25 are fixed
couplings,
such as may be obtained by welding or otherwise pernnanently joining beams 20
and 21 to beams 22 and 23, in order to obtain enhanced strength and stiffness
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under load. Beam coupling 25 may be fixed to horizontal beam 20 or 21, and
also
adjustably fixed to beam 22 or 23. Beam couplings 25 may be manufactured from,
4" X 4" X 3/8" X 6" square steel tubing, among other suitable materials.
Beams 20, 21, 22, and 23 maybe manufactured from any suitable material
having the necessary strength and resilience to withstand the loads required
during
use. One such material is steel, particularly steel tubing, although a variety
of ~ther
materials may be used. Where beams 20, 21, 22, and 23 are manufactured from
steel tubing, the steel tubing may be 3°' X 3" x 3/16" square steel
tubing_
3ig frame 12 may also include diagonal bracing straps 26 and 27 between
beams 22 and 23. Straps 26 and 27 may reinforce the rigidity of the jig frame,
and
help maintain beams 22 and 23 (and therefore beams 20 and 21) in a parallel
relationship. Straps 26 and 27 may be prepared from 2" X %" steel straps,
among a
~rariety of suitable materials_
Ro~f truss jig 10 further includes a hoist connection 16 that is utilized to
raise the entire jig above the ground, and may include any fixture or feature
that
facilitates hoisting jig frame 12. In the illustrated roof truss jig of
Figures 1-5, hoist
connection 16 includes four eyebolts 30, attached to beams 22 and 23 so as to
define the corners of a rectangle. Hoist connection 16 further includes
cabling 32,
configured to suspend eyebolts 30 from a common hook or connection 33 that
serves to lift the jig. Typically, a crane or hoist is used to lift the jig
using a hook
or ball connection. Although a greater or lesser number of connection points
to the
jig frame may be used to hoist the jig without departing from the scope of the
invention, the use of four connection points in a rectangular array offers
significant
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advantages with respect to stabilizing the load being hoisted, and so is a
preferred
configuration. The connection points are preferably symmetrically disposed
about
the center of jig frame 12', to increase stability and facilitate balanced
loading of
the jig frame.
A plurality of truss supports 14 are disposed on horizontal beams 20 and 21.
The truss supports of the invention serve to suspend individual roof trusses
from
jig frame 12 with a predetermined spacing and orientation. Any suitable means
of
suspending a roof truss from one of beams 20 and 21 is a suitable truss
support fox
the purposes of the invention. In the roof truss jig of Figures 1-5, truss
supports 14
are disposed on and coupled to beams 20 and 21. As shown in more detail in
Figure 3, truss support 14 includes bracket 34 having the shape of an inverted
U
that is disposed on beam 20. It should be understood that a plurality of such
truss
supports may be disposed on either beam 20, beam 21, or preferably both beam
20
arid beam 21. Truss support bracket 34 may be manufactured from 4" X 1/8"
steel
strap, among a variety of suitable materials.
Refernng to Figure 3, bracket 34 may be held at a preselected position on
beam 20 by a retaining bolt 36. Where it is desired to change the spacing and
orientation of the roof trusses suspended from the jig of the invention, the
particular position of bracket 34 may be changed by removing bolt 36, aligning
bracket 34 with a different predrilled hole 38 on beam 20, and inserting and
tightening bolt 36. The predrilled holes on beams 20 and 21 corresponding to
the
preselected positions for truss supports 14 are typically symmetz-ically
disposed
with respect to the center of the beam, so as to increase stability and
balanced
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loading of the jig. Any spacing between truss supports that is consistent with
the
requirements of roof truss assembly construction is an appropriate truss
support
spacing. Typically; the truss supports are spaced so as to have a distance of
approximately two feet between centerpoints of adjacent truss supports.
Typically,
a given roof truss is suspended from two truss supports disposed on beams 20
and
21, respectively.
The roof truss , jig of the invention is generally configured to suspend a
plurality of roof trusses. Typically, the roof truss jig includes sufficient
truss
supports to suspend 5 or more roof trusses. The roof truss jig may include
suff cient truss supports to suspend 7 roof trusses at a preselected spacing
of two
feet on center. Additionally, or in the alternative, the size of a particular
desired
truss assembly may not require the entire capacity of the truss jig, leaving
selected
truss supports empty during construction of the truss assembly.
'Truss support 14 fiu-ther includes a pin 40 inserted into matching apertures
in flanges 42 and 43 that form the sides of bracket 34. Pin 40 is configured
to.-span
the open end of the U of bracket 34 so that it is securely retained by the
bracket.
For example, pin 40 may incorporate a threaded segment that engages a threaded
receiver in extension 43. Alternatively, a cotter pin, locking bolt, or other
suitable
retention means may be attached to the nose of pin 40 after it is inserted
through
extension 43, to hold the pin in place. Typically, pin 40 supports and anchors
a
coupling 45 that depends from bracket 34, where the coupling.is used to
suspend a
roof truss from truss support 14.
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Coupling 45 may have a fixed or variable length, however it is preferred
that the length of coupling 45 be sufficient that a desired rbof ti-azss niay
be
suspended from jig frame 12 without contacting the jig frame. The coupling
rnay
incorporate one or more of a hook, a solid bar, a chain, a rope, a strap, or
any other
suitable means with the strength and resiliency required to suspend a desired
roof
truss from bracket 34. As illustrated in Figure 3, coupling 45 rnay include a
snap
hook 46 depending from pin 40, that in turn supports a strap of flat webbing
48,
such as nylon webbing or polypropylene webbing. Synthetic webbing is strong,
abrasion resistant; and highly flexible, and is well suited for use as a
coupling
according to the invention. Snap hook 46 may be fastened to and depend from
pin
40 by inserting the pin through an eyelet 47 of hook 46. Webbing 48, in turn,
array
be fastened to and depend from hook 46 by inserting the hook through a loop SO
of
webbing 48, where the loop is formed, for example, by durable stitching 52 of
the
webbing.
The free end of webbing 48 may be tied around a truss member of a roof
truss in order to suspend the truss from the jig. Alternatively, any suitable
hook,
loop, or buckle may be used to secure the roof truss; such as, for example, a
cam
buckle or a ratchet buckle.
Roof Construction using the Roof Truss Jig
A roof truss framework, optionally including roof sheathing, may be rapidly
and safely constructed using the roof truss jig of the present invention.
Typically,
roof truss jib 10 is assembled, at the desired work site, with the spacing
between
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beams 20 and 21, and the spacing between truss supports 14 selected so as to
accommodate the particular roof trusses t~ be used in the roof construction.
The
roof truss jig is hoisted into the air using hoist connection 16, and
suspended above
a work surface at a height sufficient that a roof truss can be freely
suspended from
the truss jig, yet remain accessible from the work surface, as shown in Figure
4.
Although the work surface is typically at or near ground level, the truss jig
of the
invention may also be used to facilitate construction of a roof truss assembly
at a
work surface above ground level, such as on an elevated platform.
A plurality of roof trusses 54 is suspended from the truss supports of roof
truss jig 10, so that the individual roof trusses have a predetermined spacing
and
orientation. Typically, each individual roof truss is suspended so that is
substantially vertically plumb and substantially horizontally level, and each
of the
roof trusses is suspended so that it is substantially aligned with each other
roof
truss.
Upon suspending and aligning the roof trusses from the roof truss jig, the
roof trusses are then braced to form a roof truss assembly. Bracing the roof
trusses
includes fastening lateral bracing 56 between individual trusses as :needed to
create
a truss assembly of sufficient strength and structural integrity for use in
the desired
roof construction. The lateral bracing optionally includes alignment bracing,
where
the alignment bracing is attached to the roof trusses either temporarily or
permanently to facilitate alignment of the trusses during construction of the
truss
assembly.
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The truss assembly may be partially or completely sheathed while
suspended from the roof truss jig. Typically, roof sheathing 58 is installed
on the
truss assembly up to the point of attachment of the truss support coupling 45.
At
this point the partially sheathed truss assembly has sufficient structural
integrity
that it may be lowered to rest on the ground, and the roof truss jig
disconnected
from the truss assembly so that the remaining roof sheathing can be installed.
While the sheathing of a first roof truss assembly is being completed, it is
particularly advantageous to move the roof truss jig to another portion of the
worksite, suspended above the work surface, so that a second truss assembly
may
be constructed. When the second truss assembly has been partially sheathed and
similarly lowered to the ground, the roof truss jig is disconnected, and then
used to
hoist the now fully sheathed first truss assembly 60 into a desired position
on a
building frame 62, as shown in liigure 5. The roof truss jig may then return
to the
fully sheathed second truss assembly and hoist it, in turn, to its desired
position.
This process represents a particularly efficient use of the roof truss jig of
the
invention, as the truss jig is in nearly constant use during construction of
the roof.
When the roof truss jig is utilized to hoist a completed truss assembly into
position, the truss jig may be reattached to each roof truss at the same
points used
during the initial suspension of the trusses. This may require creating an
aperture
in the sheathing above the desired attachment point so that coupling 45 can be
attached to the truss. Where the truss assembly is not fully sheathed, either
to
facilitate attachment of the truss jig, or because the truss assembly
represents only
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a portion of the finished roof, reattachment of the truss jig may not require
formation of an aperture in the sheathing.
Alternatively, the roof truss jig may be used to hoist the truss assembly by
attaching the truss jig at less than every original attachment point. For
example, a
sheathed truss assembly may only be connected to roof truss jig 10 at four
points,
typically corresponding to two attachment points on each of two trusses,
typically
trusses set in from the edges of the truss assembly, more typically, the
.second truss
in from each edge of the truss assembly. The additional stress on the truss
assembly during hoisting may be mitigated by using a spreader bar (not shown)
to
reinforce the truss used as an attachment point. In particular, a spreader bar
may be
placed against the bottom edge of the top chord of the roof truss,
perpendicular to
the span of the truss. When the roof truss jig is attached to the truss,
coupling 45 is
wrapped around both the truss and the spreader bar.
Through the careful selection of the particular size and configuration of
truss jig used, the roof truss jig of the invention rnay be useful in the
construction
of any type of trussed roof construction. Although , particularly useful for
construction of a gable roof, flat roofs, pitched roofs, wood framed roofs,
and
metal framed roofs may all be framed using the roof truss jig of the
invention. The
roof truss jig is suitable for use in both residential and commercial
construction
applications, although the load requirements of the truss jig may be more
severe
for commercial applications: For example, a truss jig intended primarily for
residential construction may have a load rating of 3,000 lbs, while a
commercial
truss jig may require a load rating of 5,000 lbs. Heavier load ratings may
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necessarily require .correspondingly stronger. hoist connections and couplings
so
that the increased loads can be tolerated.
The roof truss jig described herein is of substantial utility to a residential
production builder, for example, who may be responsible for constructing 2-5
homes a day. Such a, builder could typically supply a roof ta-uss jig of the
invention
to a framer and crane operator, so that they could frame the roof of a first
hame_
Upon completion of the first roof, the framer and crane operator would be able
to
proceed to a second worksite in order to frame a second roof, and so on.
Although the present invention has been shown and described with
reference to the foregoing operational principles and preferred embodiments,
it
will be apparent to those skilled in the art that various changes in form and
detail
may be made without departing from the spirit and scope of the invention. T'he
present invention is intended to embrace all such alternatives, modifications
and
variances that fall within the scope of the appended claims.
