Space frame constuction

A space frame construction of generally pentahedron pyramidal modules comprising chord members forming a rectangular base, strut members of closed tube configuration and which converge to form an apex, and flat connector plates at the apex and at the corners of the rectangular base.

PRIOR ART AND BACKGROUND OF THE INVENTION 
In U.S. Pat. No. 3,270,478 to C. W. Attwood there is defined and described 
"space frame" construction and it is therein acknowledged that the general 
concept is known to have been contemplated before from the mere geometry 
viewpoint in U.S. Pat. No. 2,433,677 to H. H. Thomas. The Attwood patent 
discloses a space frame construction which may be described as being of 
generally pentahedron pyramidal modular construction comprising open 
channel chord members, open channel strut members, and fixture plates. The 
chord and strut members are of straight and equal lengths. The fixtures or 
connector plates are of a relative complex configuration comprising 
alternate flat and inclined surfaces for receiving the chord and strut 
members, with the chord members having the open face of their channel 
cross-section facing exteriorly of the pyramid form. 
The Thomas patent discloses a roof structure comprising a plurality of 
pyramidal units each comprising straight framing members connected 
together, at the apex and the base corners, by junction members of general 
circular tubular cross-sectional shape having laterally directed screwed 
bosses to which screw couplings are connected. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is an object of this invention to provide a more simple and facile space 
frame construction which is resistant to buckling. 
It is another object of this invention to provide preformed components 
which can be easily assembled by unskilled labor to form a space frame 
construction. 
It is a further object of this invention to provide a space frame 
construction wherein the attachment of roofs, floors, and other structures 
is facilitated and which provides a more pleasing appearance, in an 
aesthetic manner, of the open frame structure when viewed from beneath the 
structure. 
Briefly, the objects are attained by and this invention contemplates the 
provision of diagonal strut members having a special configuration, 
straight chord members, and generally flat connector plates arranged in a 
combination which defines a module having a generally pentahedron 
truncated pyramidal configuration. One or more of the modules, and in some 
cases even all of them, may be assembled on the ground and then raised 
into position by a crane or other hoisting means.

DESCRIPTION OF A PREFERRED EMBODIMENT 
This invention is particularly adapted for use in the construction of 
building of roofs with load carrying structural capacity. However, it will 
be understood that the principles can be applied in any construction 
wherein the benefits of "space frame" geometry may be utilized. The space 
frame is adapted for support across a bearing support structure and for 
long span applications where intermediate supports are not needed. 
In a general sense, the space frame of this invention comprises a plurality 
of substantially parallel chord members, arranged and spaced in upper and 
lower planes, with the chords of one plane being laterally offset, in 
alternate fashion, from those in the other plane in both the longitudinal 
and transverse directions. Substantially flat connector plates are used to 
interconnect the chord members in each plane and with diagonal strut 
members. The strut members are closed tubes with distal portions of a tube 
being smoothly formed from the main body portion to present a generally 
S-shape configuration, with the distal portions being tubular, as opposed 
to being closed by flattening, and being, in respect to each other, in 
parallel planes. In a preferred embodiment, the closed tube chord and 
strut members have a square cross-sectional configuration. However, it 
will be understood that closed tubes of other configurations may be used 
so long as a flat bearing seat is provided at the distal portions for 
mating with the flat bearing surface of a connector plate; as an example 
the tube may be circular throughout a major extent of its length but with 
the distal portions being rectangular. 
In a preferred arrangement, four chord members form the base of the 
structural module, which module is in a general form of a truncated 
pyramid; the diagonal strut members of the pyramid are comprised of closed 
tubes; and flat connector plates are at each corner of the base and at the 
apex of the pyramid. 
Referring to FIG. 1 of the drawing, the space frame construction there 
shown comprises a plurality of laterally spaced chord members CL extending 
in a direction designated for purpose of description as longitudinal, with 
the chord members CL in the upper plane being further designated by the 
suffix U, i.e. CL-U, and those in the lower plane by the suffix L, i.e. 
CL-L. The chord members CL-U are laterally offset from the chord members 
CL-L. 
There is also shown, in like manner, a plurality of chord members CT 
extending in a direction transverse to the longitudinal chord members CL. 
The chord members CT are also arranged in the upper and lower planes and 
are further designated as CT-U and CT-L, respectively. The diagonal strut 
members to be later described in more detail are designated by the 
reference character D. 
In a preferred embodiment all of the chord members CL and CT are of a 
rectangular closed tube configuration and most preferably square. However, 
in some instances, some of the chord members may be of a U shaped 
cross-section, such as in selected areas where it is desired to use the 
space frame as a support for hanging units or apparatus such as lighting 
fixtures, space heaters, or the like. Usually, in such cases, it will be 
the lower chord members CL-L and CT-L from which such other items will be 
suspended and with the open end of the U members facing downward. 
As can be observed more clearly in FIG. 5, two of the chord members CL-L 
and two of the chord members CT-L, together with interconnecting lower 
connector plates PL, all being in generally the same plane, form the base 
of the generally upright truncated pyramid. It will also be observed there 
that two of the chord members CL-U and two of the chord members CT-U, 
together with interconnecting upper connector plates PU, all being in 
generally the same plane, form the base of the generally inverted 
truncated pyramid. For the sake of clarity the elements comprising the 
upright pyramid are shown in solid lines, those elements comprising the 
inverted pyramid are shown in phantom lines; and those elements common to 
both pyramids are shown in both solid and phantom lines. 
From FIG. 1 it will be observed that any two adjacent upright pyramidal 
modules are secured together by two of the base corner lower connector 
plates PL and by a chord member CL-U extending between the respective 
upper connector PU at the apexes of the pyramids. 
The connector plate P is a relatively flat member, i.e., it has no angled 
or inclined seating planes to seat the connecting chord and web members. 
In a preferred form (FIG. 3) the plate P is octagonal in plan view. The 
plate P defines a series of holes H equally spaced radially from the 
center of the plate where there is also defined a center hole CH. The 
series of holes are also equally spaced at intervals of 45 degrees about a 
circle having its center coincident with the center of the plate P. Along 
the same radial line of each hole H are coined positioning lugs L which 
are adapted to accurately position a chord member or strut member to be 
connected. The lugs along a single radial line are disposed on the same 
side of the plate in respect to each other but on the opposite side of the 
plate in respect to the lugs along a next adjacent radial line. For 
convenience of description, the lugs on the top side of the plate P are 
designated as LT and those on the bottom side as LB (FIG. 8). In FIG. 3, 
the depressions which are formed in the coining of the bottom lugs LB are 
designated by LD. The purpose of the lugs L is to mate with corresponding 
holes HL in the walls of the chord members and the strut members and thus 
accurately position the members in respect to the connector plate and to 
each other. The center hole, CH may be used to secure attachment means for 
positioning an assembled module at the construction site. 
It will be noted that the bolt receiving holes HL of the strut members D 
are on the exterior side of the tube section, in respect to a modular 
unit, and that the holes HL of the chord members C are on the interior 
side of the tube section, in respect to a modular unit. Likewise, the 
access openings AO of the strut members D are on interior side of the tube 
section and the openings AO of the chord members are on the exterior side 
of the tube section. 
The positioning of the plates within a pyramidal module is such that all of 
the strut members D are mounted interiorly of the modular units and all of 
the chord members C are mounted exteriorly of the units. Consequently, a 
top plane is presented which is level throughout its extent and which thus 
facilitates the attachment of a deck or roof. Sheeting ST or other 
material may be secured directly to the chord members C by unskilled labor 
who only need to operate a powered screw driver to insert a self-tapping 
screw S in forming a connection as shown in FIG. 9. In contrast, in 
installations where open channels are used as the top chords or struts 
more complex fastening systems are required to secure roofing or other 
deck construction; for example a skilled welder may be needed to arc weld 
sheeting to the chord members and in other installations additional 
structural members, such as wooden plate members, may be required. 
In a preferred space frame arrangement, one of the connector plates P 
secures four chord members C and four strut members D, with each member 
being accurately positioned by two positioning lugs L and being fastened 
by a single bolt B. As may be seen in FIG. 7, the head BH of the bolt B is 
in an elongate form and dimensioned in respect to the inside of the tube 
to be secured such that upon insertion through access opening AO and after 
initial turning the bolt head BH will interference fit and press against 
the walls of the tube and cease rotating upon further tightening of the 
nut N. Consequently, only a single wrench or tightening tool is required 
for the nut. In contrast, in systems where the dimensions of the bolt head 
are all less than the spacing between the sidewalls of the tube, two tools 
are required, one to hold one of either bolt or nut, another to rotate the 
other of either bolt or nut. Also, an opening larger than that to merely 
permit insertion of the bolt head would be required in order to 
accommodate the holding or tightening tool. The unthreaded shank portion 
UT is accurately dimensioned in respect to the mounting hole HM of the 
tube and the corresponding hole of the connector plate H to facilitate, 
together with the positioning lugs, the transmission of the shear or 
tensile stresses. 
The nut N has a counterbore portion CB adapted to receive a part of the 
unthreaded shank portion UT of the bolt and thus insures that upon full 
tightening of the nut N the corresponding chord or strut member will bear 
tightly against the connector plate. 
In one of the preferred embodiments, designated as a five foot module, the 
spacing of the connector plates is five feet from center to center of the 
plates at the four corners of the square base of the pyramid; the height 
from the plane extending through the outside surface of the square base to 
the plane extending through the outside surface of the connector plate at 
the apex of the generally pyramidal form (truncated) is three feet ten 
inches; the tubes forming the chord and the strut members are 15/8 inches 
square, outside dimensions; the over-all length of the tube strut along 
its centerline line is about 601/4 inches, with the distal straight 
portions each being about 31/2 inches long. It is also preferred to use an 
inside radius of at least 3 inches in forming the legs of the S-shape of 
the tube struts in order to minimize bulging and to provide a smooth curve 
transition from the diagonal straight length to the distal legs, which 
legs are in parallel planes. 
The use of the strut members of this invention having a closed tube 
cross-section and a generally S-shaped configuration, with the distal 
portions being generally parallel to each other, results in a number of 
advantages. The thickness and/or cross-sectional dimensions of the web 
members may be less than that employed in web members which are of an open 
cross-section such as a U-shaped channel. The explanation for this is that 
the closed section is more resistant to twisting or torsion stresses. For 
example, if it be assumed for comparison purposes that the closed tube and 
open channel both be fabricated of 12 gauge material (0.105 thickness) and 
in the same square shape, 15/8 inches on a side, the theoretical angle of 
twist, due to the same degree of applied torque, for the open channel 
would be in the order of 180 times as great as that for the closed tube. 
With the same dimensional and applied torque assumptions, the shear stress 
would be in the order of 23 times as great for the channel as it would be 
for the closed tube. 
Further, by reason of the distal portions being in planes which are 
generally parallel to each other, relatively simple flat connector plates 
may be used. Such plates are distinct from those which are necessarily of 
complex configuration because of the need to match all of the different 
diagonal planes in which the distal portions of generally straight linear 
strut members converge at the connector plates forming the corners and 
apexes of the pyramidal units. A further advantage of the use of the flat 
connector plates and generally S-shaped strut members is that only one 
type of connector plate is required for the system. In contrast, in 
systems where connector plates having diagonally extending bearing seats 
with two positioning lugs positioned on the same face thereon, two 
different types of plates are required, usually designated as in-strut and 
out-strut connectors; the in-strut connectors having their positioning 
lugs on the inside faces of their angled seats and the out-strut 
connectors have their positioning lugs on the outside faces of their 
angled seats. The connector plates of this invention are also distinct and 
provide an advantage over connector plates having diagonally extending 
bearing seats with a positioning lug on each side of the plate portion 
forming the bearing seat. While this latter described arrangement is such 
that the same connector plate may be used in either the top or bottom 
planes, only one of the positioning lugs is used at one end of a strut 
member; in contrast, in this invention two positioning lugs are used at 
each end of a strut member to better facilitate exact positioning of the 
strut member between two connector plates. 
The positioning of the chord members on one side of the connector plate and 
the diagonal strut members on the opposite side of the plate provides an 
arrangement wherein the twisting forces are better balanced as compared to 
arrangements wherein all of the members, chord and strut, are secured to 
the same side of the connector fixture. 
A still further advantage of the system of this invention is that the 
height of the pyramid form need not be restricted even if the size of the 
base of the pyramid be maintained. Consequently, the system is more 
readily adapted for use in conjunction and combination with pre-existing 
structures. In contrast, those systems which employ structural elements 
which are all of the same length, including the diagonal or strut members, 
are limited to a fixed height. Also, those systems which employ connector 
plates having angled bearing seats for the strut members are also limited 
to a fixed height. With the present system changes in height can be 
accommodated simply by varying the angle and length of the straight linear 
portion between the distal portions of the S-shaped strut members.