Note: Descriptions are shown in the official language in which they were submitted.
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STRUCTURAL FRAMEWORK AND WEBS THEREFOR
BACKGROUND OF THE INVENTION
The present invention relates to a framework including reinforcing webs and to
the
reinforcing webs.
Structural frameworks of the type to which the present invention generally
relate
are typically found in buildings and commonly take the form of trusses or
braced wall
panels. Trusses come in several forms with two typical forms being a pitched
truss (e.g., a
roof truss) and a straight or parallel chords truss (e.g., a floor truss).
Trusses are formed
with chords having webs connected thereto to reinforce the truss. Braced wall
panels are
similarly constructed, but used in an orientation where the chords or "beams"
extend
generally vertically. Over the years, webs have evolved from lumber cut to
shape and
length and toe nailed into place. Later, such wooden webs were joined with
nailing plates
having integral nails. Currently, all metal webs with integral nailing plates
pressed into
the sides of the chords are used to construct some trusses (particularly flat
trusses). The
evolution of webs and their securement has improved both the efficiency in
manufacture
and the structural integrity of the formed truss.
During the construction of trusses using wood webs and separate nailing plates
or
metal webs with integral nailing plates, the set up of the truss forming
machine is time
consuming and critical since it is necessary to set up the jig with reaction
pads or pedestals
for use in driving the nailing plates into the webs and/or chords. Further,
when the truss
uses wood webs and separate nailing plates, each web has to be custom cut
(although the
webs may be mass produced to a unique configuration) and positioned by hand to
effect
installation which is time consuming and therefore costly. Further, as the
price of wood
has increased, metal webs have become more economically attractive. The metal
webs
that are pressed into the sides of the chords, unlike wood webs that fit
between inside
edges of the cords, may sometimes make stacking of the trusses difficult
because the webs
have portions that project from the opposite faces of the chords. There is
thus a need for
an improved metal web that fits between inside edges of the chords like wood
webs.
SUMMARY OF THE INVENTION
Among the several objects and features of the present invention may be noted
the
provision of a metal web that will fit between the beams of a structural
framework; the
provision of such a web that can be easily secured to the beams; the provision
of such a
web having a single configuration useable on a variety of frameworks with the
same
configuration; the provision of such web that can be economically made and
used; and the
provision of a structural framework utilizing such a web.
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A metal web member of the present invention is
preferably for use in a fabricated framework comprising at
least two spaced apart beams with transverse thickness and
having exterior surfaces and at least one web member secured
to the beams and extending between generally opposed exterior
surfaces of the beams. The web member comprises a support
section having transverse width substantially equal to or
less than the transverse thickness of the beams and having
opposite ends. A tab extending longitudinally from the
support section at each end thereof has planar engagement
surfaces. Each tab is sized and shaped for generally flat,
face-to-face engagement of its planar engagement surface with
a respective one of the exterior surfaces of one of the beams
for the tab securement thereto. The tabs are further adapted
to receive a fastener through the planar engagement surface
for the securement of the web member to the beams.
According to one particular aspect of the
invention, there is provided a metal web member for use in a
fabricated framework comprising at least two spaced apart
beams with transverse thickness and having exterior surfaces
and at least one web member secured to the beams and
extending between exterior surfaces of the beams, said web
member comprising: a support section having transverse width
substantially equal to or less than the transverse thickness
of the beams and having opposite ends; and a tab extending
longitudinally from the support section at each end thereof
and having planar engagement surfaces, each tab being sized
and shaped for generally flat, face-to-face engagement of its
planar engagement surface with a respective one of the
exterior surfaces of one of the beams for securement of the
tab thereto, said tab having transverse width substantially
equal to or less than the transverse width of the support
section, said tab being further adapted to receive a fastener
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through the planar engagement surface for the securement of
the web member to the beams; and a transition section which
merges each tab with the support section of the web member,
the transition section having a pair of ridges on each side
of the web member defining respective valleys, each ridge
angling laterally outwardly from a position adjacent the
support section to a position adjacent the tab.
There is also provided a metal web member for use in
a fabricated framework comprising at least two spaced apart
beams with transverse thickness and having exterior surfaces
and at least one web member secured to the beams and extending
between exterior surfaces of the beams, said web member
comprising: a support section having transverse width
substantially equal to or less than the transverse thickness
of the beams and having opposite ends; and a tab extending
longitudinally from the support section at each end thereof
and having planar engagement surfaces, each tab being sized
and shaped for generally flat, face-to-face engagement of its
planar engagement surface with a respective one of the
exterior surfaces of one of the beams for securement of the
tab thereto, said tab being further adapted to receive a
fastener through the planar engagement surface for the
securement of the web member to the beams, the support section
including a deformation adjacent the tab, the deformation
having a pair of ridges defining a valley therebetween, each
ridge angling laterally outwardly from a position adjacent the
support section to a position adjacent the tab.
In another aspect of the present invention, a
method of constructing a structural framework for a building
comprises the step of providing first and second beams at
least partially spaced apart, each beam having
longitudinally extending exterior surfaces. At least one
metal web is provided for interconnection between the first
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and second beams. The web has a support section and a tab
extending outwardly from generally adjacent each end of the
support section. Each tab is formed to have a planar
engagement surface and a fastener hole extending through the
planar surface. The tabs at each end of the support section
of the metal web are arranged for flat, face-to-face
engagement with one of the exterior surfaces of a respective
one of the first and second beams such that the support
section extends at an angle with respect to the first and
second beams. The tabs are secured to the beams by passing
a fastener through the fastener hole of each tab and into
said respective one of the first and second beams.
There is also provided a method of constructing a
structural framework for a building, the method comprising
the steps of: providing first and second beams at least
partially spaced apart, each beam having longitudinally
extending exterior surfaces; providing at least one metal web
member for interconnection between the first and second
beams, the web member being formed of a tube and having a
longitudinal axis, a support section and a tab extending
outwardly from generally adjacent each end of the support
section, the transverse width of the support section defined
by a diameter of the tube, each tab being formed to have a
planar engagement surface and having a fastener hole
extending through the planar surface, the web member having a
transition section which merges each tab with the support
section of the web member, the transition section having a
transverse width equal to or less than the transverse width
of the support section and having a pair of ridges on each
side of the web member defining respective valleys, each
ridge extending at an angle relative to the longitudinal axis
such that each valley extends from a narrower end at a
position adjacent the support section to a wider end at a
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position adjacent the tab; bending the tabs to a first angle
relative to the longitudinal axis of the web member; bending
the tabs at each end of the support section of the metal web
member to a second angle different from the first angle for
flat, face-to-face engagement with one of the exterior
surfaces of a respective one of the first and second beams
such that the support section extends at an angle with
respect to the first and second beams; and securing the tabs
by passing a fastener through the fastener hole of each tab
and into said respective one of the first and second beams.
In yet another aspect of the present invention, a
tool for driving a screw through a web and into a beam of a
structural framework for a building comprises a tool head
having an engaging portion for engaging a head of a screw to
rotate the screw and drive the screw into the work piece in
a direction parallel to the longitudinal axis of the screw.
A drive shaft is arranged transverse with respect to the
intended direction of driving of the screw into the work
piece. A drive transmission between the drive shaft and the
20) engaging portion transmits rotary drive from the drive shaft
to the engaging portion. The drive transmission is
constructed to limit the torque applied by the tool head to
the screw.
In still another aspect of the present invention, a
die tool forms a securing tab on a metal web to be used in
forming a structural framework for a building. The die tool
includes a bottom die tool having a squash block and a capture
block, the squash block being moveable relative to the capture
block. A top die tool has a squash block moveable relative to
a capture block. A guillotine block is moveable relative to
squash blocks and the capture blocks to cut the web. The web
is retained by the capture blocks and the
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squash blocks are moved relative to the capture blocks so as to squash the end
of the web
so as to form a flattened portion of the securing tab. The guillotine block is
moved relative
to both the capture blocks and the squash blocks so as to cut lateral edge
portions from the
flattened portion of the securing tab.
Other objects and features will be in part apparent and in part pointed out
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a standard pitched roof truss with four webs extending between
the
chords with the web members being of the general type shown in Fig. 5;
Fig. 2 shows a truncated pitched roof truss showing the use of a pair of web
members of the type shown in Fig. 11C;
Fig. 3 shows a parallel chords truss illustrating the use of web members of
the
general type shown in Fig. 5;
Fig. 4 is a perspective of a web member of the type shown in Figs. 10A-10E;
Fig. 4A is a perspective of an adjustable length web member similar to the
fixed
length web member of Fig. 4;
Fig. 4B is an elevation of a truss incorporating the adjustable length web
member
of Fig. 4A;
Fig. 5 is a perspective of a web member of the type shown in Figs. 11A-11F
that
provides a plurality of interconnected web member sections;
Fig. 6 is an enlarged cross section of a web member and insert taken along the
line
6-6, Fig 5;
Fig. 7 is an enlarged fragmentary side view of a web member of the type shown
in
Figs. 11 A-11 F;
Fig. 8 is an enlarged fragmentary side view of a web member similar to Fig. 7
but
showing a different shape of notch in a side wall;
Fig. 9 is an enlarged fragmentary side view of a web member similar to Figs. 7
and
8 but showing a still different shape of notch in a side wall;
Figs. l0A-l0E are side views of a range of different lengths of web members of
the
type depicted in Fig. 4, for example 600, 900, 1200, 1800, 2 100 mm long;
Figs. 11A-11F are side views of the type of web member with multiple
interconnected sections of the type shown in Fig. 5 with section lengths of
600 plus 1200,
900 plus 1200, 1200 plus 1200, 1200 plus 1800, 1200 plus 2100 and 1800 plus 2
100 mm
long as examples;
Fig. 12 is a perspective of a reinforcing member for use as shown in Figs. 13
and
14;
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Fig. 13 is an enlarged section view of the web and reinforcing member taken
along
the line 13-13, Fig. 14;
Fig. 14 is a perspective of a web member with an installed reinforcing member;
Fig. 15 is an enlarged fragmentary side view of the connection of web members
to
top and bottom chord members of a pitched roof truss;
Fig. 16 is an enlarged fragmentary perspective of a pitched roof truss showing
forward and reverse bends in the web member;
Fig. 16a is a further enlarged fragment of Fig. 16, but showing a web member
having an ear to augment attachment;
Fig. 17 is a side elevation of a modified form of a web member made from a
tube;
Fig. 18 is an enlarged, fragmentary portion of the modified web member of Fig.
17
at a central portion;
Fig. 19 is an enlarged, fragmentary portion of an end of the modified web
member
of Fig. 17;
Fig. 20 is a fragmentary portion of a web member configured for greater
strength if
of a longer span using a capping member;
Fig. 21 is a side elevation with reference to load direction (horizontal load
direction) of a structure having timber studs braced by webs in accordance
with the present
invention; and
Fig. 22 is an enlarged, fragmentary perspective view of the arrangement
showing
part of the structure as shown in Figure 21.
Fig. 23 is a side view of a metal web for a building truss, shown broken in
the
middle, according to an embodiment of the invention;
Fig. 24 is a plan view of a left end of the web of Figure 23;
Fig. 25 is a cross-sectional view along the line 25-25 of Figure 24;
Fig. 26 is a view along the line 26-26 of Figure 25;
Fig. 26A is a plan view of an extension piece which can be used with the
embodiment of Figs. 24 to 26;
Fig. 26B is a side view of the extension piece of Figure 26A;
Fig. 27 is a view of a building truss using metal webs of the type described
with
reference to Figs. 23 to 26;
Fig. 28, 29 and 30 are enlarged, fragmentary views of portions of the truss of
Fig.
27;
Fig. 31 A, 31 B, 31 C, 31 D, 31 E and 31 F show various different tab
configurations
which can be used in the present invention;
Fig. 31 G is a plan view of a part of a web according to a further embodiment
of the
invention;
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Fig. 31H is a side view of the part of the web of Figure 31G;
Fig. 3 11 is an end view of the part of the web of Figure 31G;
Fig. 31J shows the web of Figure 31G applied to a chord of truss;
Fig. 32 is an enlarged, fragmentary view showing one preferred manner of
5 connecting a metal web to a chord of a truss;
Fig. 33 is a perspective view of part of a metal web according to a further
embodiment;
Fig. 34 is a side view of a completed metal web according to the embodiment of
Figure 33
Fig. 35 shows a still further embodiment of the invention;
Fig. 36 is a perspective view of an extension and/or strengthen member used in
one
embodiment of the invention;
Fig. 37 is a bottom plan view of the member of Figure 36;
Fig. 38 is a side view of the member of Figure 36;
Fig. 39 is a schematic cross-sectional view of a driving tool used to fasten
the
metal webs according to the preferred embodiment to a chord of truss;
Fig. 40 is a view of a bottom die tool used in forming the metal webs
according to
Figs. 23 to 26;
Fig. 41 is a cross-sectional view through the tool of Figure 40;
Fig. 42 is a cross-sectional view along the line 42-42 of Figure 41;
Fig. 43 is a perspective of a capture block used in the tool of Figure 40;
Fig. 44 is a plan view of the capture block of Figure 43;
Fig. 45 is a perspective of a squash block used in the embodiment of Figure
40;
Fig. 46 is a plan view of the squash block of Figure 45;
Fig. 47 is a perspective of groove block used in the tool of Figure 40;
Fig. 48 is a plan view of the groove block of Figure 47;
Fig. 49 is a perspective of a top die tool (shown in an inverted position to
that in
which it would be used) which is used with the tool of Figure 40 to form a
complete tool
for forming metal webs according to Figs. 23 to 26;
Fig. 50 is a view of the top die of Figure 49 as shown in a compressed
condition;
Fig. 51 is a cross-sectional view through the die of Figure 50;
Fig. 52 is a cross-sectional view through the line 52-52 of Figure 51;
Fig. 53A is a perspective view of a guillotine tool used in the top die of
Figure 50;
Fig. 53B is an end view of the guillotine tool of Figure 53A;
Fig. 53C is a side view of the guillotine tool of Figure 53A;
Fig. 53D is a plan view of the tool of Figure 53A;
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Fig. 54 is a view showing the commencement of the formation of a metal web of
the type shown in Figs. 23 to 26, using the tool formed from the die tools of
Figure 40 and
Figure 50;
Fig. 54A is a fragmentary elevation of the metal web in initial condition
before
formation from the tool as shown by Figure 54;
Figs. 55 and 55A, Figs. 56 and 56A, Figs. 57, 57A and 57B and Figs. 58 and 58A
schematically show a sequence of operations of the tool of Figs. 40 and 50,
and the web as
it is being formed during those sequence of steps; and
Fig. 59 is a view of a screw used in the preferred embodiment.
Corresponding reference characters indicate corresponding parts throughout the
several views of the drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The reference numerals 21A, 21B, 21C designate generally three different
styles of
truss, 21A being a pitched roof truss (Fig. 1), 21B being a truncated pitched
roof truss
(Fig. 2) and 21C being a parallel chords truss (usable, e.g., as a floor
truss)(Fig. 3). Truss
21A comprises a pair of sloped top chords 23 joined at the apex 25 and a
bottom chord 27
joined to the top chords 23 adjacent lower ends of the top chords with,
nailing plates 31.
The chords are broadly referred to herein as "beams". The truss 21A is
generally
triangularly shaped. The truss 21B is similar to the truss 21A except it has a
truncated top
formed by a horizontal top chord 35 extending between and secured to the
chords 23 with,
e.g., nailing plates 31. The truss 21C comprises top and bottom chords 37, 39
and can be
provided with generally vertical end posts 41 secured to the chords 37, 39
also with nailing
plates 31. The chords 23, 27, 35, 37, 39 have inside edges 23E, 27E, 35E, 37E,
39E at
least partially defining interior spaces 43A, 43B, 43C for the trusses 21A-C
respectively.
The width of the inside edges is the transverse thickness thereof and of the
trusses. The
chords 23, 27, 35, 37, 39 and posts 41 also have opposite side faces 23S, 27S,
35S, 37S,
39S,41 S respectively lying in generally parallel planes for each of the
trusses. Preferably
the chords are wood, for example so-called 2X4's (nominally 1-1/2" X 3-1/2").
For the
trusses 21A, 21B, the narrow surface (1-1/2") is typically the inside edge,
while for a
parallel chords truss 21C, the wide surface (3-1/2") is typically the inside
edge. However,
it is to be understood that the chords could be made of metal without
departing from the
scope of the present invention.
A formed metal web member is provided and is secured to and extends between at
least two chords of a truss. Three forms of web members are shown, the form in
Figs.
1 0A-10E, the form in Figs. 11A-11F and the forms in Figs. 17 and 23. All
forms have
common features and will be first described in regard to the form shown in
Figs.,4 and
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10A-10E, all being the same construction except for dimensions. A web member
51
includes an elongate bottom wall 53 having opposite ends and opposite side
edges.
Preferably, the wall 53 is generally planar. At least one side wall and as
shown, a pair of
side walls 59L, 59R extend upwardly from the wall 53 at the side edges and
form a central
support section 58. The walls 59 are generally parallel and preferably
generally normal to
the wa1153 and form an open sided channel with the wall 53. The walls 59 have
opposite
ends 61L, 61R that are preferably contoured as by rounding or in other
suitable shapes. A
fastening tab 63 extends from each of the opposite ends of the central support
section. The
tabs 63 have generally planar oppositely facing surfaces with one or more
apertures 67
extending therethrough. The web member is preferably metal, e.g., steel,
galvanized for
rust resistance and has a suitable thickness such as about 0.85 mm. The width
W of the
tab 63 is approximately equal to or slightly less than the width of the inside
edge of the
chord to which the web member is to be secured. The length L of the tabs 63 is
about
35mm and their width is about 20mm in the illustrated embodiment. The spacing
between
the walls 59 is approximately equal to the width W of the tabs. The height of
the walls
will be determined by the resistance to bending needed in web member and in
one
embodiment are in a range of about 50mm to 70mm. The web member 51 can be made
from flat sheet material and cut to shape and then roll formed or bent on a
brake to form
the walls 59. When completed, the bottom wall 53 is generally planar as are
the walls 59.
The walls 53, 59 are one piece with each other and form an open ended channel.
An adjustable length web member 51' having a basic construction similar to the
web member 51 of Fig. 4 is shown in Figs. 4A and 4B. Corresponding parts of
the web
member 51' will be designated by the same reference numerals used for the web
member
51 of Fig. 4, followed by a prime. The web member 51' includes two web
elements 51A'
and 51B', each having the channel shaped construction of Fig. 4, but including
a tab 63' at
only one end. The web member 51B' is inverted from the position of web member
51A'
and inserted into the open end of the web member 51A' opposite the end having
the tab
63'. The overall length of the web member 51' is determined by the lengths of
the web
elements 51A' and 51B', and how far element 51B' is inserted into 51A'. When
the
desired overall length is achieved, the web elements 51A' and 51B' are secured
together
by pairs of sheet metal screws S driven through the bottom wall 53 of the
element 51A'
and the bottom wal153' of the element 51B'. Preferably a short piece of lumber
L is
placed in the overlapping section of the web elements 51A' and 51B' for
enhancing the
connection of the screws S. Once the length is set, the web member 51' is used
in the
same way as web member 51 for conventional trusses, as shown in Fig. 4B, or
for wall
bracing. The web member 5 1' has the advantage being able to be adjusted in
length so that
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the angle of the tab 63' can be controlled so that it does not interfere with
the end of the
support section 58'.
The web member 71 (Figs. 5, 11 A-11 F and 14)is similar to the construction of
the
web member 51. The web member 71 is essentially a series of two or more
connected
webs 51 wherein a plurality of central support sections 58 are connected
together. The
connection is provided by a common tab 63 attached to and extending between
adjacent
end-to-end web central support sections. Two or more sections may be provided.
A series
of web members 71 are shown in Figs. 11A-11F, each being comprised of a
connected pair
of support sections 58. The truss of Fig. 3 illustrates a web 71 with four
support sections
58 connected by tabs 63. The sections 58 may be formed separately and secured
together
but in the preferred embodiment, are formed form the same piece of material,
so that the
tabs 63 of adjoining sections are not structurally distinct. Notches 73 (Figs.
7, 8 and 9) are
defined by the adjacent contoured ends 61 of the sections 58 and allow bending
of the tabs
63 in both a forward direction (the ends 61 L, 61 R on opposite ends of a
notch move closer
together) and a rearward direction (the ends 61L, 61R on opposites ends of a
notch move
apart) for securement of a web member to chords as described hereinafter. The
notches 73
allow for easy bending at the tabs 63 and prevent interference between the
ends of the
walls 59 when the bend is a forward bend.
A modified form of web member is shown in Figs. 17-19 with parts similar to
the
parts of the web 71 being shown with a prime superscript for clarity. The web
71' is
formed from a tube 81 with the tabs 63' being formed by deforming (flattening)
a short
length of the tube. An aperture 67' is formed in the tab 63'. In this
embodiment, the
sidewalls 59L', 59R' are the more upright portions of the perimeter of the
tube. The
bottom wa1153' is the lowermost portion of the tube perimeter. The web member
71' has a
top wall portion 83 which is the uppermost portion of the perimeter of the
tube.
Preferably, the tube is generally round in transverse cross section except in
the deformed
areas forming the tabs 63'. However, the tube may have other cross sectional
shapes, such
as rectangular or oval, without departing from the scope of the present
invention.
During loading of an open top (channel shaped) web member 51 or 71 in
compression, the side walls 59L, 59R may deflect toward or away from one
another. A
slight inner directed curvature could be provided in the side walls to induce
inward
deflection during compression loading. A reinforcing member 85 is provided to
resist
such deflection and is illustrated in Figs. 12, 13, 14. The reinforcing member
85 has a pair
of flanges 87 connected to and projecting generally at right angles from a
central
connecting wa1189. The outer surfaces 91 of the flanges 87 are spaced to
snugly fit
between the inside surfaces of side walls 59 for a friction fit therebetween.
The flanges 87
are each provided with an elongate outwardly opening groove 95 extending along
the
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length of the member 85 at a position adjacent the junction between the
central wall 89
and the flanges 87. When a reinforcing member 85 is installed in a web member
51 or 71,
the grooves 95 are adjacent free edges of the side walls 59. The flanges 87
have a height
substantially equal to the height of the wall 59 so that an outside surface of
the flanges is
flush or slightly above flush with the free edges. The side walls 59 are bent
to form
inwardly directed protuberances 101 (Fig. 13) that can be in the form of
longitudinally
extending ribs or localized ridges or dimples spaced along the length of the
side walls.
The protuberances 101 project into the grooves 95 for releasably retaining the
member 85
in the support section of the web member 51 with a snap lock connection. An
aperture
105 can be provided in the central wall 89 for the attachment of laterally
extending
intertruss braces or additional web members to sections (not shown) of the web
member
71 or between web members 51 for additional bracing.
Reinforcing member 85 can be utilized once or at several different positions
on
longer spans. There may be a case for providing a more aesthetic box section
for longer
sections while at the same time providing a greater measure of rigidity. If
desired the web
member can be provided with, for example, the in turned flange type forms 59'
depicted in
Figure 20. These flange like forms 59' can be complemented by appropriate
flanges 86 of
a capping member 85' which can (if desired) run for the full extent or
substantially the full
extent of the web member. The flanges 86 bear against the flange like forms
59' to retain
the capping member 85' in place. It is within the scope of the present
invention to connect
the capping member 85' to the web member by fasteners or by welding (not
shown). The
side walls of the web member of Fig. 20 are formed with ribs 88 to further
increase their
strength.
In the construction of a truss, the various chords are joined together in any
suitable
manner to form the perimeter shape of the truss. The desired web member 51, 71
or 71' is
selected and the tabs 63' are bent relative to the central support sections to
overlie and
engage the inside chord edges, e.g., 23E, 27E, for attachment at predetermined
locations
therealong. Referring to Figs. 15, 16 and 16A, web member 71 is secured to at
least two
chords by driving a fastener 107, such as a screw fastener, through each of
the apertures
67, of the tabs 63. The fasteners 107 have enlarged heads 108 that each
overlie a
respective tab. A washer 109 may be provided for each fastener 107 to help
stiffen and
strengthen the tabs 63, to reduce bending or fastener tear through and is
captured between
a respective head 108 and tab. The longitudinal axis of each of the fasteners
107 lies in a
plane generally parallel to the plane of the respective truss 21A-C formed by
the chords.
The plane of a truss (Fig. 16) is a plane extending between opposite ends of
the truss and
bisecting the truss between the opposite side faces, e.g., 23S, 27S.
Alternatively, the truss
may be considered as including two planes, each including respective side
faces 235, 275
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of the chords 23, 27. The longitudinal axis of the fastener 67 is also
generally parallel to
the opposite side faces, e.g., 23S, 27S of a chord into which they are
screwed. If desired,
additional fasteners may also be used to secure the side walls 59 of the web
members 51,
71 where they overlap the side edges of the chords. The lengths of the central
support
5 sections of the web members are preferably sized so that the tabs 63, will
be located on the
chords at desired locations for appropriate bracing of the chords. The notches
73 can be
formed by removal, e.g. cutting, of material from the sheet material from
which the web
member 71 is made. In an alternate embodiment, the sheet may be cut to form
the end
edges of the side walls 591eaving the material connected at one edge to the
tab 63 to form
10 an ear 111 (see Fig. 16A) which may also be used to help secure the web
member to a
chord with an additional fastener 107. The ear 111 is bent down over the side
275 of the
chord 27 as shown in Fig. 16A. Such an arrangement would be useful when there
is
insufficient room in the inner space 43 to use a fastener driver.
Referring now to Figs. 21 and 22, web members 51, 71 of the present invention
are
shown as employed in a wall frame 90 including a top plate 90a, a bottom plate
90b and
studs 90c extending between the top and bottom plates. In this embodiment,
adjacent
studs constitute the first and second beams. The web members 51, 71 extend
generally
from side to side instead of top to bottom as when used in trusses. The web
members 51,
71 brace the wall frame 90 against lateral or shearing forces on a wall of a
building, such
as may be experienced during an earthquake or in high winds. The web members
51, 71
may be secured to the studs 90c in the same way as they are secured to the
chords of the
trusses described above.
With reference to Fig. 23 a metal web 300 for a building truss T shown in Fig.
27
is closely related to the metal web 71' shown in Figs. 17-19 above. The metal
web 300 is
formed from a metal tube 301 which is preferably of generally circular cross-
section. The
metal tube 301 may form a complete cylindrical structure and be formed in a
rolling
process with edges of the blank from which the tube 301 is formed being welded
or
otherwise joined together to form a tube 301 having a continuous circular or
cylindrical
wall. However, it is to be understood that tubes (not shown) of non-circular
cross section
may be used without departing from the scope of the present invention. In
other
embodiments the tube 301 can be rolled so that edges of the blank from which
the tube is
formed are merely adjacent one another without being joined together thereby
forming a
longitudinal slot which extends the length of the tube. The web 300 can be
formed in
stock lengths commencing at a length of 300 mm with stock lengths increasing
in length
by 150 mm up to a maximum length of 2900 mm. These stock lengths are merely
exemplary and obviously other stock lengths and increments could be used if
desired.
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The web 300 has securing tabs 302 formed at least at one end. In the preferred
embodiment each end has a securing tab 302 as clearly shown in Fig. 23. The
manner in
which the securing tabs 302 are formed will be described in detail hereinafter
with
reference to Figs. 40 to 58. The securing tab 302 comprises a generally flat
tab portion
304 which has a hole 305 for receiving a fastening screw S (see Figs. 28 to 30
for
example). The tab portion 304 is formed symmetrically with respect to the
cylindrical
tube 301 as is best shown in Fig. 23.
The flat tab portion 304 merges into the tube 301 at a transition section 306.
The
flat tab portion 304 is generally formed by diametrically opposed semi-
cylindrical surface
portions of the tube 301 by squashing or flattening those portions together as
will be
described with reference to Figs. 40 to 58. The transition section 306
comprises opposed
valleys 308 which extend axially inwardly from the tab portion 304 and merge
with a
deformed part 301a of the tube 301. Each valley 308 is located between a pair
of ridges
309 (as best shown in Fig. 24) which incline outwardly from the tab portion
304 to the non
deformed portion 301a of the tube 301. As best seen in Fig. 24, the valleys
308 taper from
a generally wide entrance portion 310 to a narrower end portion 311 with the
entrance
portion 310 being adjacent the tab portion 304 of the tab 302. Each pair of
ridges 309 has
side walls 312 which merge with the floor 307 of the valley 308. The side
walls 312 are
joined by a curved transition wall 312a.
Ends of the ridges 309 adjacent tab portion 304 have sloping end surface
portions
313 which slope down to the tab portion 304. Tab portion 304 has a neck 304a
which
projects inwardly to the entrance 310 of the valley 308 and the floor 307 of
the valley 308
inclines upwardly from the end of the neck 304a to the wa11312. The walls 312
in
cross-section transverse to the longitudinal axis of the web 300 are slightly
rounded so as
to form a relatively smooth transition from the ridges 309 to the wall 312 and
then into the
floor 307 upon deformation of the tube 301 to form the valleys 308 and ridges
309, as best
shown in Fig. 25.
As is clearly shown in Fig. 24 the tab section 304 is no wider in the
direction of
double headed arrow W1 in Fig. 24 than the diameter of the tube 301. Thus the
tab section
304 is within the confines of the tube 301 and does not project radially or
diametrically
beyond the tube 301. This is important in the formation of building trusses
because it
enables the chords of the building truss to be the same size as the diameter
of the tube 301,
or alternatively, the tube 301 to be the same size as the chords of the
building truss, so that
the web 300, and in particular the tab portion 304, does not project beyond
the planes of
the chords of the building truss. This prevents interference with other
framing or building
components of a building to which the building truss is to be used and
facilitates stacking.
The manner in which the tab portion 304 is retained within the confines of the
tube 301 so
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it does not project beyond the diameter of the tube 301 will also be described
in detail with
reference to Figs. 40 to 58. The transition between the flat tab portion 304
and the sloping
surfaces 313 of the ridges 309 form a hinge line 314 along which the tab
section 304 can
bend relative to the tube 301 to angle the tab section 304 at a predetermined
angle with
respect to the tube 301 for flat, face-to-face engagement with a chord of a
building truss.
Figures 26A and 26B show an extension piece 600 which can be used with the
embodiment of Figs. 23 to 26. The extension piece 600 is formed from a tubular
member
601 which has an internal diameter slightly greater than the external diameter
of the web
300 so that the tube 601 can slide over the web 300 (including the tab 302).
The tube 601
is formed with a tab 602 which is identical in configuration to the tab 302
previously
described except that it is slightly larger because of the slightly larger
diameter of the tube
601. The tube 601 is provided with a plurality of holes 603 along its length
and the tube
301 of the web 300 can also be provided with a number of holes (not shown)
along its
length at least adjacent the tabs 302. Alternatively, the web 301 could be
provided with a
single hole. In still an alternative arrangement, the extension piece 600
could be provided
with a single hole 603 and the tube 301 of the web 300 provided with a number
of holes
along its length adjacent the tab 302. In a most preferred embodiment, the
extension
piece 600 is provided with one or more holes 603 and the tube 301 has no
holes. The
extension piece 600 is located in the desired position on the tube 301 and a
self tapping
screw is driven through the hole 603, forming its own hole in the tube and
securing the
tube 301 and extension piece 600 in the desired position.
The extension piece 600 enables the length of the web 300 according to Figs.
23 to
26 to be adjusted by sliding the extension piece 600 over the tab 302 and onto
the tube 301
of the web 300 at one of the ends of the web 301. The extension piece 600 is
then secured
in place by locating a screw through one of the holes 603 of the extension
piece 600 and
into a hole in the tube 301 of the web 300 so as to securely fasten the
extension piece 600
at the required position on the tube 301 to extend the length of the web 300
to a desired
length. The extension piece 600 may have a length of, for instance, about 400
mm. This
embodiment of the invention enables the length of the webs 300 to be extended
by use of
only a single piece and therefore decreases the number of stock lengths which
may be
required and also the number of components which are required in order to form
a web
300 of a required length. The extension piece 600 provides a substantially
infinite
adjustment of the length of the web 300 by sliding the extension piece
relative to the tube
301.
Fig. 27 shows a building truss T according to one embodiment of the invention
which includes metal webs 300 of the type described with reference to Figs. 23
to 26. The
truss T has a bottom chord Tl and upper chords T2 and T3 which are arranged
at,oblique
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angles with respect to the chord T1. Webs 300 extend between the chords Ti and
T2 and
T3 as shown. As best shown in Fig. 28 the tab portion 304 has been bent an
angle of
almost 90 so that it will lay flat against surface T3' of the chord T3.
Figures 29 and 30
show details of how tab portions 304 are bent at desired angles so that they
will lay flat
against the other chords Tl and T2 to enable securement of the webs 300 to the
chords Tl,
T2 and T3.
The tab portion 304 is bent relative to the tube 301 by abutting the tab
portion
against part of the chord T1 and moving the tube 301 so as to bend the tab
portion about
the hinge line 314. The wall thickness of the tube 301 is relatively thin and
therefore the
tab 304 itself is relatively thin and can be bent relatively easily by manual
force if desired.
In other embodiments the tab portion section 304 could be already provided
with a slight
bend in one direction or the other so as to facilitate more easy bending of
the securing
section 304 to the desired angle relative to the tube 301 for location flush
with a chord T1,
T2 or T3.
As particularly shown in the more detailed Fig. 30, the webs 300 do not
actually
come into contact with one another or abut one another at positions where they
meet the
chords T1, T2 or T3. In conventional wooden trusses it is usual that the
wooden webs
solidly abut and contact one another at positions where they are joined to the
chords T1,
T2 or T3. The reason for this is that the contact of the webs with one another
takes some
of the load applied through the chords T1, T2 and T3 and therefore distributes
the load
through both of the webs to or from the chords T1, T2 or T3. However, in
accordance
with the preferred embodiment of the present invention the securing tab 302 is
designed to
operate in isolation in both compression and tension. The securing tab 302
which joins the
webs 300 to the chords T1, T2 and T3 is sufficiently strong to take all of the
required load
and therefore does not require the webs 300 to contact one another. Indeed,
the webs can
be spaced apart at their connections with the chords T1, T2 and T3 as is best
shown in Fig.
30. The ability of being able to space the webs 300 from one another, rather
than having
them contact one another as in conventional wooden trusses, makes it easier to
install the
webs 300 in place and overcomes problems associated with precise lengths to
ensure that
webs do contact one another at the positions where they are joined to the
chords T1, T2 or
T3.
As previously described, the metal webs 300 are secured to the chords T1, T2
and
T3 by self tapping screws S which are driven through the holes 305 in the tab
portions
304 and screw into the wooden chords T1, T2 and T3. The preferred manner in
which the
self tapping screws S are driven into the chords TI, T2 and T3 to secure the
webs 300 in
place will be described hereinafter with reference to Fig. 39 and the
preferred structure of
the screws S will be described with reference to Fig. 59.
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Figures 31A to 31F show various tab configurations which may be embodied in
the
invention. In these Figures, rather than the tab 302 being symmetrical with
respect to the
tube 301, the tab 302 is formed to lie generally adjacent one peripheral
portion of the tube
301 from which the web 300 is formed. In Fig. 31A the tab 302 has the tab
portion 304
formed as a right angle having portions 304b and 304c with the portion 304b
being
adjacent inside edge T3' of chord T3 and the portion 304c being adjacent side
T3' of the
chord T3. The tab 302 is secured to the chord by a screw S passing through the
opening
305 (not shown in Figs. 31A-31F) in the tab portion 304 and the side T3" into
the chord.
Figure 31C shows the web 300 of Fig. 31B but fixed in a position with the tube
301 rotated 180 about its longitudinal axis with respect to the tube 301
shown in Fig.
31B. It will be understood that in Fig. 31B the web 300 lies entirely outside
the planes of
the chord T3' and in Fig. 31 C the web lies entirely inside of the planes of
the chord.
Figure 31D is a view similar to Fig. 31A except that the portion 304b is
somewhat
shorter thereby locating the tube 301 slightly higher relative to the chord T3
than the
position shown in Fig. 31A. Figure 31E is a view of a web 300 similar to that
shown in
Fig. 31D except located on the face of the chord T3 opposite to the face T3".
In other
words, the configuration of Fig. 31D is simply rotated 180 .
Figure 31F shows an arrangement where the two opposed peripheral portions of
the tube 301 which are compressed together to form the tab portion 304 are
separated into
two parts 304e and 304f so as to form a generally U-shaped channel
configuration into
which the chord T3 is located. A pair of screws S pass through holes similar
to the hole
305 in the separate portions 304e and 304f to secure the web 300 to the chord
T3.
The various embodiments with reference to Figs. 31A-31F show different tab
configurations which can be used to locate the web 300 at a desired position
relative to a
chord T3 should it be desired to provide the web 300 other than totally within
the confines
of the chords T1, T2 and T3 to, for example, provide additional space for
other framing or
component which may be used in the building.
Figures 31G to 31J show a still further embodiment of the invention in which
the
tube 301 is formed with a tab 302 which comprises a first gusset 609 and a
second gusset
610. The gussets 609 and 610 are formed by slicing the tube 301 substantially
parallel
with the longitudinal axis of the tube 301 and flattening the two sliced
portions of the tube
301 to form the gussets 609 and 610. The portion of the tube 611 adjacent the
gussets 609
and 610 is then deformed in a somewhat similar manner to that described with
reference
Figs. 23 to 26 so as to form a valley 615 on diametrically opposed sides of
the tube 301
between the gussets 609 and 610. The valley 615 inclines outwardly from the
gussets 609
and 610 to merge with the undeformed part of the tube 301.
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Figure 31K shows the manner in which the web of Figs. 31G to 3 11 is applied
to a
chord (for example the chord T1). The gussets 609 and 610 are applied over the
chord T1
so that the gussets 609 and 610 sandwich the chord Tl. The gussets 609 and 610
are each
provided with at least one hole 616 and screws S are applied through the hole
or holes 616
5 to join the gussets 609 and 610 to the chord T1.
Figure 32 shows one embodiment of how the tab portion 304 is attached to a
chord
T1. In this embodiment a washer 320 (substantially identical to washer 109,
described
above) of generally square or rectangular configuration is utilized and which
sits on the tab
portion 304. The tab portion 304 may have upstanding walls 321, 322 and 323
which
10 form a housing in which the washer 320 locates. The walls 321 may have
flanges 326
which are bent over after location of the washer. The walls 321, 322 and 323
prevent
rotation of the washer 320 as the screw S is driven into the chord T1 to
connect the web
300 to the chord T1. In other embodiments the tab 304 can be flat as described
with
reference to Fig. 23 and a separate box housing section (not shown) could be
located
15 beneath the tab portion 304 for receiving the washer 320 to hold the washer
in place
during driving of the screw S into the chord T1. In these embodiments the tab
304 or the
separate box housing retains the washer in the required orientation shown in
Fig. 32, that
is with the washer parallel to the chord T1 so that it does not spin or
project outwardly
beyond the limits of the chord T1, thereby speeding up assembly of trusses
according to
this embodiment of the invention.
As is clearly shown in Fig. 32, the washer 320 is relatively thick and extends
for
substantially all of the length of the tab portion 304. Thus, the washer 320
extends from
the hinge line 314 described with reference to Fig. 24 to the free end of the
tab portion
304. The washer 320 provides additional strength to the connection of the web
300 to the
truss T and also additional strength of the tab 302. If the web 300 is
tensioned, that is
force is applied in the direction of arrow F in Fig. 32, the washer 320 will
resist the
tendency to lift the tab portion 304 from the chord Tl at the position of the
tab portion 304
which extends between the screw S and the hinge line 314 which defines the
transition
between the tab portion 304 and remainder of the web 300.
Figures 33 and 34 shown an embodiment of the invention in which the web 300 is
formed from a tube 301' as shown in Fig. 33. The ends of the tube 301' are not
deformed
to produce the tabs 302 previously described. Rather, in this embodiment,
extension
pieces 340 (see Fig. 34) are formed and have the tabs 302 formed at one end.
The
extension pieces 340 each include a sleeve into which a respective end of the
tube 301' is
inserted. The extension pieces 340 are fastened in place by a screw 341 which
passes
through a hole (not shown) in the extension piece and also a hole 343 in the
tube 301'. In
this embodiment a number of holes (not shown) may be provided along the length
of the
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tube 301' so that the web 300 can be adjusted in length by securing the
extension piece 340
to a desired one of the holes 343 or in a desired position along the row holes
343 to
provide a web 300 of a desired length. This embodiment has the advantage of
being easily
able to adjust the length of the web 300 with the disadvantage that the web is
formed from
at least two different components thereby increasing the amount of stock
required in order
to form the web 300. Thus, this embodiment may reduce the number of stock
lengths
which must be retained in order to form building trusses at the expense of
requiring
additional components to form a completed web 300.
Figure 35 shows a further embodiment in which the web 300 has an auxiliary
connection member 350. The web 300 may be formed in the manner described with
reference to Figs. 23 to 26 with the securing tab 302 secured to chord T1 (for
example) in
the manner previously described. In this embodiment washer 320 is merely
located on top
of the tab portion 304 and the screw S secures both the washer 320 and 304 to
the chord
T1. The auxiliary connection portion 350 can serve either or both of the
functions of,
extending the length of the web 300 (in which case the tab portion 304 may not
be secured
to the chord T1) and providing additional strength of the connection of the
web 300 to the
chord T 1.
The auxiliary connection portion 350 comprises a U-shaped section 351 which
has
holes (not shown). The section 351 may be semi-circular in cross section and
formed from
a part tubular member. The section 351 has a connection tab 354 formed at one
end by
flattening out the section 351, or alternatively, by merely forming the
section 351 into the
curved configuration from a blank whilst maintaining the portion 354 in the
flat
configuration.
The tube 301 of the web 300 is provided with a row of holes (not shown) and
the
section 351 is connected to the tube 301 by screws S2 which pass through the
holes in
section 351 and locate in holes (not shown) in the tube 301. The portion 354
has a pair of
holes (not shown) which receive screws S3 to attach the auxiliary connection
member 350
to the chord T 1.
Thus, if additional connection strength of the web 300 to the chord T1 is
required
the web can be connected by the securing section 340 and the auxiliary
connection
member 350. If it is desired to increase the length of the web 300 then the
connection
member 350 can be coupled to the tube 301 at a desired position along the
length of the
tube 301. In that event, the web 300 would be connected to the chord Tl solely
by the
portion 354 and the screws S3.
Figures 36, 37 and 38 show a further embodiment of an extension member or
strengthening member 360. In this embodiment the member 360 has a generally
part
tubular section 361 which has two opposed rows of holes 363 and 364 formed
along its
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length. At one end of the section 361 a pair of connector paddles 365 are
formed. The
paddles 365 may be formed by forming a cut along part of the length of the
section 361
and flattening out those parts of the section to form the paddles 365.
In this embodiment the remainder of the web 300 can be formed in the manner
described with reference to Figs. 23 to 26 or simply from a tubular member
301' as shown
in Fig. 33. The member 360 can be secured to the tube 301 by sliding the tube
into the
U-shaped profile of the section 361 and adjusting the position of the section
361 relative to
the tube 301 so that a desired one of the holes 363, 364 register with a hole
at the end of
the tube 301. A screw can then be inserted through the aligned holes to secure
the member
360 to the tube 301. A member 360 can be attached to the other end of the tube
301 in the
same manner if desired. The formed web 300 is then attached to a chord by
locating the
paddles 365 on opposed sides of the chord and hammering nails or driving a
screw
through holes 366 in the paddle members. This embodiment of the invention
provides the
ability to extend the length of a web 300 and also additional strength because
of the two
paddle sections 365 which attach to the chord.
Figure 39 shows a driving too1370 for driving the screws S through the holes
305
in tabs portions 304 to connect the metal webs 300 to chords T1 to T3 of a
building truss
T. The too1370 comprises a tool head 372 having a sleeve 374 which extends
generally
perpendicular to the axis of the screw S and the direction the screw S will be
driven into
the chords T. The sleeve 374 encloses a drive shaft 376. The drive shaft 376
may be
connected to a motor (not shown) for rotating the shaft 376. The motor may be
contained
within a housing having a suitable hand grip section and actuation button for
supplying
power to the motor for rotating the shaft 376.
The shaft 376 has a bevel gear 377 attached to its end. The bevel gear 377 is
contained within an upper cavity within the head 372. The bevel gear 377
meshes with a
second bevel gear 379 also contained within the upper cavity. A socket 380 is
received in
a middle cavity and is a generally snug fit in the middle cavity but having
sufficient
tolerance to rotate within the cavity. The socket 380 has a neck portion 382
which is
connected to the bevel gear 379. The bevel gear 379, neck 382 and socket 380
may be
formed as an integral unit. The socket 380 has a socket recess 383 for
receiving head H of
the screw S. The socket recess 383 has a magnet 385 is adhered or otherwise
attached to
the closed end of the socket recess.
The cavity 379 is also in communication with a generally square shaped lower
cavity. A magnet 386 is located in the lower cavity and is attached to top
wall 387 of the
cavity. The top wall 387 has an opening 388 which communicates the middle
cavity with
the lower cavity and generally allows the screw S to pass through the cavity
so the head H
can be received in the socket recess 383. The magnet 386 has a central opening
389 which
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registers with the opening 388 to also allow the screw S to be received in the
socket recess
383.
Bottom surface 390 of the magnet 386 defines a surface against which washer
320
can sit. The screw S and washer 320 are formed from a ferromagnetic material
and the
magnet 385 serves to hold the head H of the screw S within the socket recess
382 so that
the head is retained above the washer 320 within the socket recess 382. The
magnet 386
holds the washer 320 within the recess 384. Thus, the screw S and the washer
320 can be
applied to a hole 305 of a tab portion 304 to connect the tab portion 304 to a
truss chord
T1, T2 or T3 without the need of a workman to hold the screw S in place as the
screw S is
positioned and screwed down into the chord T.
The distance between a lower extremity 394 of the socket 380 and the bottom
surface 390 is provided and dimensioned so as to prevent over tensioning of
the screw S
when the screw is driven into the chord T1. If the screw S is over driven when
it is
applied to the chord T1, T2 or T3 the over driving can strip out wood fibre
from the chord
and reduce the effective load on the connection screws. This can cause
structural failure.
In the embodiments shown the bottom surface 390 of the magnet 385 spaces the
washer 320 from the lower extremity 394 of the socket 380. However, if a
greater space is
required, or a smaller thickness magnet used, a spacer member (not shown)
could be
located against the lower surface 390 of the magnet 386 provided that the
magnet is still
able to provide sufficient magnet attraction to hold the washer 320 in the
recess 384. The
spacer would have a central hole similar to the magnet 386 to enable the screw
S to pass
into the socket recess 382.
Furthermore, it should be noted that the washer 320 is held in the required
orientation in the square lower cavity so that when the tool is applied to the
screw S the
washer 320 is parallel with the chord Tl and does not project beyond the
extremities of the
chord Tl. Thus, the washer 320 will be applied to the chord T1 in the required
orientation
(such as that disclosed with reference to Fig. 32) without the need for manual
intervention,
thereby speeding up assembly of trusses.
As will be explained in further detail hereinafter, the over tensioning of the
screw S
into the truss chord Tl is prevented because when the screw S is rotated by
the socket 380
and driven into the chord Tl, the screw S will eventually leave the socket
recess 382 and
the head H will locate in the space between the lower extremity of the socket
380 and the
top of the washer 320. The space between the lower extremity and the top of
the washer
320 may be dimensioned to completely acconunodate the head H so that the head
H leaves
the socket recess 382 or, alternatively, the space may be slightly smaller
than the height of
the head H so that a small part of the head H still remains within the socket
recess.
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When the screw S is to be applied to a portion 304 the tool 370 is actuated so
as to
rotate the shaft 376 to rotate the socket 380. Rotation of the socket 380 will
rotate the
screw S. It should be understood that the washer 320 will remain in a fixed
position
within the recess 384 because of the square shape of the recess 384 and
corresponding
shape of the washer 320. Thus, the screw is screwed down or into a timber
truss chord T1
due to rotation of the screw S. As the screw S is driven into the chord T1,
the bottom
surface of the washer 320 will eventually contact the surface of the chord T
into which the
screw S is being driven. When this occurs continued rotation of the screw S
will cause the
screw S to continue to be driven into the chord T with the head H beginning to
leave the
socket recess 382. When the head H abuts the top surface of the washer 320 the
head H is
accommodated within the space between the upper surface of the washer 320 and
the
lower extremity of the socket 380. If at this point the head H has completely
left the
socket recess 382 then obviously drive is no longer supplied to the screw S
and therefore
the screw S is not over driven into the chord T1. In other words, as soon as
the head H
screws down onto the top surface of the washer 320, the driving force or
torque applied to
the screw S is discontinued and therefore the screw is firmly screwed into the
chord Tl but
is not over driven into the chord T1.
If the space between the lower extremity of the socket 380 and the top of the
washer 320 is such that the head H does not completely leave the socket recess
382, which
is preferred, the head 382 will project only a very small distance into the
recess 382 which
is sufficient to provide driving torque to the screw S to continue driving of
the screw S
when the head H contacts the top surface of the washer 320. If any part of the
head is
retained in the washer 326 it will simply be slightly rounded off by rotation
of the socket
380 because the engagement between the socket recess 382 and the head H is no
longer
sufficient to impart rotational torque to the screw S. The rounding off will
not adversely
effect the head H as it will be merely a slight rounding at the very uppermost
portion of the
head H. Thus, the integrity of the head H will remain in case it is necessary
or desired to
unscrew the screw S from the chord T1.
The right angled configuration of the drive shaft 376 with respect to the
screw S
and driving direction of the screw S is advantageous. This enables the head
372 to be
positioned as close as possible to the transition between the portion 304 and
the tube
portion 301 of the web 300, while keeping the axis at rotation of the socket
380
perpendicular to the face of the chord T1 through which the screw will be
driven. This, in
turn, enables the hole 305 to be positioned as close as possible to the tube
301.
Positioning of the hole 305 as close as possible to the tube 301 provides the
advantage of
reducing the bending moment which will be applied to the screw S during
tension loading
of the web 300. If the hole 305 is spaced a large distance from the tube 301
thenthe
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amount of leverage which will be applied to the screw S when tension is
applied to the
web 300 is greatly increased thereby increasing the possibility that the screw
can be pulled
out of the chord T 1 by that applied tension force. The right angled
configuration of the
head 372 enables the head to be positioned close in against the tube 301 and
yet
5 perpendicular to the adjacent face of the chord, which may not be possible
in all
circumstances if the tool 370 had a drive shaft 376 are co-axial with the
screw S. In such
cases it may be necessary to position the screw S further from the tube 301,
because of the
confined space and interference with the tube 301 which may occur in some web
configurations within a building truss thereby providing the disadvantages
discussed
10 above.
Figures 40 to 58 show a die tool for forming the tabs 302 on webs 300 in
accordance with the preferred embodiment of Figs. 23 to 26. The die tool
comprises a
bottom tool die 400 shown in Fig. 40 and top tool die 500 shown in Fig. 49. In
use the top
tool die 500 shown in Fig. 49 is inverted from the position shown in Fig. 49
and laid over
15 the top of the bottom tool die 400 shown in Fig. 40 as will be shown in
more detail with
reference to Figs. 54 to 58.
With reference to Figs. 40 to 42 die 400 comprises a base plate 401. The plate
401
has bores 403 for receiving pins (such as pins 411) which are used to locate
components of
the tool 400 and allow movement of the components relevant to one another as
is usual in
20 die tools. The base plate 401 also has bores 405. A squash block 406 (shown
in more
detail in Figs. 45 and 46) is mounted on the base 401 and retained in place by
pins (not
shown) which locate in bores 403 and in corresponding bores in the block 406.
The block
406 is fixed stationary relative to the base 401 and therefore the pins serve
only to hold the
block 406 in place and not allow movement of the block 406 relative to the
base 401. As
best shown in Figs. 45 and 46 the squash block has a raised squash surface 407
and a pair
of lower surfaces 408. A groove 410 is formed in the block 406 from the squash
surface
407 down to base 409 of the block 406. Returning to Figs. 40-42, a capture
block 412 is
mounted for relative movement to plate 401 by springs 414 which locate in the
bores 405
and which extend into bores 416 in the capture block 412. The springs 414 bias
the
capture block 412 above the plate 401 as is best seen in Fig. 41.
As best shown in Figs. 43 and 44 the capture block 412 has an upper surface
417
which is provided with a semi-cylindrical groove or channel 418 which matches
the
profile of the tube 301 from which the web 300 is to be formed. A groove 420
is formed
in the capture block 412 and extends from the channel 418 to the base 421 of
the capture
block 412. When the capture block 412 is mounted on the base 401 as shown in
Figs. 40
to 42 the groove 420 registers with the groove 410 of the squash block 406.
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21
A groove block 425 which is best shown in Figs. 47 and 48 is inserted into the
grooves 410 and 420. The groove block 425 is of generally monolithic
configuration
having side walls 427 and 428. The side walls 427 and 428 are joined by an end
wall 429
and a shorter rounded opposite end wa11430. An inclined valley forming surface
432
extends from the upper end of the wa11429 to the upper end of the wal1430. The
configuration of the surface 432 is the reverse of the configuration of the
valley 308 which
is made in the tab 302 of the web 300 formed by the surface 432. The surface
432 has a
generally U-shaped inclined wall portion 434 which will form the walls 312 and
tension
wal1312a of the valley 308, a flat surface 435 which will form the floor 307
of the valley
308 and a inclined end surface 438 which will form the surfaces 314 and
entrance 304a of
the valley 308. When the groove block 425 is located into the grooves 410 and
420, the
wal1429 is located in the groove 410 and the opposite end wa11430 is received
in the
groove 420.
Figure 49 shows the top die too1500. The top die tool 500 is similar to the
bottom
die too1400 in that it has a base plate 501, a squash block 506 and a capture
block 512.
The blocks 506 and 512 are configured the same as the blocks 406 and 412
previously
described except that the block 506 has only a flat squashed surface 509. A
groove block
525 of the same configuration as the groove block 425 is located in grooves
510 and 520
of the blocks 506 and 512 in the same manner as the block 425 is located in
the blocks 406
and 412 of Fig. 40. The top die too1500 is spaced from the base plate 501 by a
compression block 519 of polyurethane or like material. The compression block
519 also
extends beneath and supports the squash block 506 as can also be seen in Fig.
51. The
block 512 is spaced from the plate 501 and the block 519 by springs 514 as
best shown in
Fig. 51. It should understood that the configuration shown in Fig. 49 shows
the springs
514 completely compressed with the block 512 sitting on the compression block
519.
A guillotine block 550 is fixed to the base plate 501 and surrounds the squash
block 506. As best shown in Figs. 53A, 53B, 53C and 53D the guillotine block
includes
side walls 521 and 522 and end wall 523. The walls 521, 522 and 523 generally
form a
U-shaped configuration as best shown in Fig. 53D so the guillotine 520 can be
positioned
about the squash block 506 as best shown in Fig. 49. The walls 521 and 522
carry knife
edges 560 and 561 at their upper extremities. The knife edges 560 and 561 are
inclined
with the knife edge 560 inclined upwardly from wa11523 to end 562 and the
knife edge
561 inclined downwardly from wall 523 to end 563. The walls 521 include bores
555 for
receiving pins (not shown) to secure the guillotine block 520 to the base
plate 501. Once
again, the guillotine block 520 is positioned in place without the need for
movement
relative to the plate 501. As shown in Fig. 49 the squash block 506 has a
central bore 570
which locates a tubular punch 571. When the squash block 506 and capture block
512 are
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22
in their starting positions where they are biased away from base plate 501 by
the springs
514, the punch 571 is retained within the bore 570. When the blocks 506 and
512 are in
their fully compressed condition, when not only the springs 514 are fully
compressed but
the compression block 519 is also fully compressed, the punch 571 projects out
of the
block 506 as can be seen in Fig. 50.
The sequence of operations for forming the tabs 302 of the webs 300 shown in
Figs. 23 to 26, will be described with reference to Figs. 54 to 58. In order
to configure the
tool shown in Figs. 40 to 53, the top die tool 500 is inverted from the
position in Figs. 49
and 50 and arranged above the too1400 as shown in Fig. 54. The plates 401 and
501 are
connected to a press machine (not shown in the drawings).
As shown in Fig. 54, the unformed tube 301 (Fig. 54A) which is to be used to
form
the web 300 is inserted into the cylindrical cavity defined by the two grooves
418 and 518
in the capture blocks 412 and 512. In the position in Fig. 54 the blocks 512
and 412 are
biased away from their respective plates 501 and 401 by springs 514 and 414
(which are
not shown in Fig. 54 for ease of illustration). In this configuration the
groove blocks 425
and 525 are retained fully within the grooves 410, 420 and 510, 520
respectively.
Similarly, the knife edges 560 and 561 of the guillotine 520 are retracted
from (that is
above in Fig. 54) the squash surface 509 of the squash block 506. Figure 54A
shows the
tube 301 in this position where the tube 301 has not yet been acted upon and
is in its
original condition.
Figure 55 shows first movement of the plates 501 and 401 towards one another
under the influence of the pressing machine (not shown) so as to capture the
tube 301 (Fig.
55A). In this position the tube 301 is still not acted on but is merely
captured and tightly
held within the cylindrical space defined by the grooves 518 and 418.
Continued
movement of the pressing machine will cause the springs 514 and 414 to begin
to
compress allowing the capture blocks 412 and 512 to move towards their
respective base
plates 401, 501. This movement moves the capture blocks 412 and 512 relative
to their
respective groove blocks 425 and 525 so the groove blocks now begin to project
into the
cylindrical space defined by the channels 418 and 518 through the grooves 420
and 520
and work on the tube 301. Simultaneously, the squash blocks 406 and 506 also
begin to
project beyond the capture block and begin to squash the end of the tube 301.
As shown
in Figs. 56 and 56A this begins to form the end of the tube 301 to commence
formation of
the tab 302. The squash blocks 406 and 506 are beginning to squash the end of
the tube
301 to form the tab portion 304 of the tab 302 and the groove blocks 525 and
425 are
beginning to form the valley 508 and ridges 509 of the tab 302. It will be
understood at
this stage of operation the guillotine knife blades 560 and 561 are still
retracted behind the
surface 509 of the squash block 506.
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23
Continued movement of the press machine brings the base plate 401 against the
bottom of the capture block 412 so that springs 414 are fully compressed.
Similarly, the
capture block 512 is now resting on the compression block 519. This movement
has
brought the squash surfaces 509 and 407 of the blocks 506 and 406 fully
together to
squash the end of the tube 301 to form the tab portion 304 of the tab 302. In
this position
the guillotine blades 560 and 561 as well as the punch 571, are still retained
behind the
surface 509 of the squash block 506. It will be apparent from the
consideration of Figs.
57A and 57B that in the squashing of the end portioin of the tube 301 to form
the tab
portion 304, bulges 304g are formed at the side edges of the flat tab portion
304. As will
also be apparent from the consideration of Figs. 57 and 57A, the groove blocks
425 and
525 now project into the cylindrical space formed by the grooves 420 and 520
to their
maximum extent thereby fully forming the valley 308 and ridges 309 of the tab
302.
As shown in Fig. 58, continued movement of the press machine will begin to
move
the base plate 501 relative to the capture block 512 and squash block 506 by
compressing
the compression block 519. As the compression block 519 is compressed, the
guillotine
550 and the punch 571 are moved relative to the squash block 506 so that the
knife edges
560 and 561 are brought down to bear on the flat securing section 304 of the
tab 302
adjacent the bulges 304g thereby slicing the bulges 304g from the flat tab
portion 304 to
only leave the flat securing section 304 as shown in Fig. 58A Simultaneously,
the punch
571 punches the hole 305 through the tab portion 304 as it is driven out of
bore 570 in the
squash block 506. It should be understood that the step or space provided
between the
squash surface 407 of the block 406 and the surfaces 408 provide room for
movement of
the knife blades 560 and 561 of the guillotine 520 and also a accommodate the
bulges
304g which are formed during flattening of the tube 301 by the squash surfaces
407 and
509. The press machine can then be released to retract the plates 501 and 401
away from
one another so that the formed web 300 can be removed.
As will be apparent from the above description of the manner in which the
securing
tab according to the embodiment of Figs. 23 to 26 is formed, the formation of
the valley of
the valley 308 by the groove blocks 425 and 525 has the effect of pushing
material down
towards the center of the tube thereby preventing outward expansion of the
tube at this part
of the web during flattening to form the tab portion 304. Slicing of the
bulbous or lateral
edge portions 304g from the edges of the flattened portion 304 has the effect
of ensuring
this part of the formed securing tab does not extend beyond the periphery of
the tube 301
of the web 300. Further still, removal of the bulges 304g takes away a
considerable
amount of material from the side edges of the tab portion 304 and therefore
makes it easy
to bend the tab portion to the required position so that the tab portion can
rest flat against
the required surface of a chord as described with reference to Figs. 27 to 30.
If the bulges
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304g are left in place not only will this mean that the securing tabs would
extend beyond
the periphery of the tube 301 but also a substantial mass of material is left
which would
make it very difficult, if not impossible, to bend the flattened tab portions
304 to the
required angle so that they can sit flush against the chords of a truss during
assembly of a
truss.
In the preferred embodiment of the invention the tab portion 304 is bent
during
assembly of the truss without the need for any tool. The tab portion 304 can
be bent by
pushing an end of the tab portion 304 against the chord and then applying a
force to the
web 300 so as to cause the tab portion 304 to bend. Alternatively, the tab
portion 304 can
be bent by application of the screw S through the tab and into the chord so
that as the
screw S is driven into the chord the screw S contacts the tab portion to bend
the tab portion
into the desired configuration. If desired, the tab portion 304 can be
provided with a slight
bend to facilitate the further bending of the tab portion either by
application of the screw
or by force applied to the web 300 and engagement of the tab portion with the
chord.
Thus, according to the preferred embodiment of the invention no tool at all is
required in order to bend the tab portion 304 thereby simplifying assembly and
reducing
the cost of assembly because of the need not to provide any particular tool to
bend the tab
portion. In practice, a single pressing machine may carry a number of die
tools of the type
described with reference to Figs. 40 to 58 so that a number of webs 300 are
formed in a
single operation. Furthermore, both ends of the web 300 can be formed within
the press
machine or in separate press machines simultaneously so as to form the entire
web 300 in
a single operating sequence.
Figure 59 shows the preferred structure of a screw S used in the embodiments
previously described. The screw S has a head H including an integral flange or
washer
portion H' and a shank S' which is screw threaded in a conventional manner.
The shank S'
and its screw threading is of the conventional self tapping style. The shank
S'joins with
the flange H' of the head H by a transition section 650 which tapers outwardly
so as to
form a region of increased thickness 651 between the shank S' and the washer
portion H'
of the head H. This increases strength of the transition between the head H
and shank S,
preventing breaking of the head H from the shank S' when load is applied to
the screw S.
In conventional screws the shank S joins with the head H at a generally right
angle step
transition with no variation in thickness that the transition between the
shank S and the
head H. Thus, the head H is susceptible to breakage underload.
When introducing elements of the present invention or the preferred
embodiment(s) thereof, the articles "a", "an", "the" and "said" are intended
to mean that
there are one or more of the elements. The terms "comprising", "including" and
"having"
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are intended to be inclusive and mean that there may be additional elements
other than the
listed elements.
In view of the above, it will be seen that the several objects of the
invention are
achieved and other advantageous results attained.
5 As various changes could be made in the above constructions without
departing
from the scope of the invention, it is intended that all matter contained in
the above
description or shown in the accompanying drawings shall be interpreted as
illustrative and
not in a limiting sense.
