Curvilinear structural insulating panel and method of making the same

A curvilinear structural insulating panel that is comprised of a plurality of slotted beam members that are deformed to a preselected radius or radii of curvature, end beam members that connect to the slotted beam members at their ends and flexible sheets that connect to the beam members and provide a hollow, air filled panel, and a method for making the same.

The present invention relates to structural insulating panels, being more 
particularly directed to a structurally strong, thermally insulating panel 
taking the form of an arc of preselected size and radius, adapted for 
connection with surrounding similar curvilinear panels and a surrounding 
support structure. 
In the accepted construction of insulating structures, rigid panels or 
bricks are secured along their edges to form planar insulating walls. 
Structures particularly useful for translucent and thermal insulating 
qualities are described, for example, in my prior U.S. Letters Pat. Nos. 
2,981,382 and 3,024,880; most suitable for planar construction panels. 
Design considerations often suggest or require, however, the use of a 
non-planar insulating wall. 
Present methods for simulating curved or non-planar insulating walls 
include securing planar panels or bricks such as hollow glass bricks and 
panels together with wedge shaped spacers (often mortar or presized 
spacers) to form a faceted approximate arc-segment, pseudo-curvilinear 
insulating wall. Such a faceted wall structure is not, however, truly a 
smooth curvilinear wall and requires the use of substantial fitted spacer 
materials that may lack the required insulating characteristics thereby 
making the entire wall structure less than an optimal insulator. 
Presently, to form a truly curvilinear panel or wall of panels, rectilinear 
panels or bricks of insulating material, such as plastic insulating foams 
or foam-glass, are joined at their edges and the entire wall structure is 
cut, milled or ground to form a curvilinear wall surface. Alternatively, 
the panels or bricks are cut, milled or ground to have a curvilinear face 
and subsequently matched, fitted and joined to form a curvilinear wall 
structure. Both methods are unnecessarily complex and costly. 
Additionally, such a wall has numerous irregularities from the non-uniform 
cutting and fitting operations and the open cellular structure of the 
foamed materials. Although coatings of mastic or covering sheets can be 
secured to the surfaces of the wall, this requires an additional, 
expensive and non-insulating operation. Finally, due to the nature and 
construction of the materials being used, such cut-foam walls are 
generally opaque to light transmission and therefore inhibit radiational 
heating through the panel or wall of panels. 
A third method of producing a structural insulating wall requires the 
standard construction of two walls that are separated by space, and the 
filling of that space by an insulating material, such as fiberglass or 
plastic foam. Such a wall is opaque to heat and light and susceptable to 
infestation by insects, rodents and other pests. Additionally, such a wall 
requires substantial construction and design skill to create a curvilinear 
wall of preselected arc and a separate operation to install and provide 
the insulating means. 
The present invention provides a method for readily-producing structural 
insulating panels of preselected arcs of curvature that may be translucent 
or transparent to heat and light radiation, and can be easily joined to 
other panels to make a curvilinear structural insulating wall of 
preselected specification. It is therefore an object of the invention to 
provide a new and improved curvilinear structural insulating panel that is 
not subject to the limitations of prior panels and may be constructed in 
the form of an arc of preselected dimensions. 
Another object is to provide a method of creating a panel that can be 
deformed to a preselected arc without bends or kinks in the materials and 
reduction in structural integrity. 
A further object is to provide a novel panel that can be easily joined or 
connected to other similar panels to form a curvilinear structural 
insulating wall; and one that provides a structural insulating panel that 
is easily reproducable. 
A still further object is to provide a novel panel that inhibits pest 
infestation during use. 
Other and further objects will be explained hereinafter and are more 
particulalry delineated in the appended claims. 
In summary, from one of its aspects, the invention embraces an insulating 
curvilinear panel structure having, in combination, a panel frame bounding 
a portion of a curve and formed by a pair of spaced similarly curved 
I-beam members joined between their ends by a pair of straight I-beam 
members; each curved I-beam member being formed by a pair of oppositely 
directed similarly curved T-shaped beam members having the long portions 
of the T's slotted into tabs and overlapped and joined together with the 
slots of each of the pair of T-shaped beam members deformed to accomodate 
the curve and staggered with respect to the slots of the other of the pair 
along the arc of their curve; and insulating cover sheet materials formed 
as a curvilinear outer and inner coaxial surfaces adhered to the 
corresponding outer and inner cross portions of the I-beams that serve as 
load-bearing edge surfaces of opposite sides of the frames. 
Preferred details and method of construction are hereinafter explained.

Referring now to FIG. 1, the letter P refers to a curvilinear structural 
insulating panel made in accordance with the present invention having 
curved I-beam members formed of pairs of oppositely mounted parallel 
T-beams 1, 2, and 3, and 4, each having a series of successive tabs 
T.sub.1, T.sub.2, and T.sub.3, and T.sub.4, respectively, comprising the 
long portions of the "T" and successively separated by slots S as will be 
discussed in more detail hereinafter. In the formation of a panel P, beam 
members 1 and 3 are bent such that the load bearing cross portions L.sub.1 
and L.sub.3, respectively, of the beams 1 and 3 extend along the outer 
radius of curvature of the panel P, with the tabs T.sub.1 and T.sub.3 
extending inwardly towards the center of the radius of curvature. T-beam 
members 2 and 4 are disposed oppositely to respective T-beam members 1 and 
3 and are similarly curvedly bent such that the load bearing cross 
portions of the "T", L.sub.2 and L.sub.4, respectively, of the beams 2 and 
4 extend along the inner radius of curvature of the panel P, with the tabs 
T.sub.2 and T.sub.4 extending outwardly (upwardly in FIG. 1 from the 
radius of curvature. When the beams 1 and 3 are curvedly similarly bent, 
the tabs T.sub.1 and T.sub.3 are curvedly deformed and are forced into 
closer proximity in direct proportion to the radius of curvature of the 
panel P and the distance from the load bearing portions L.sub.1 and 
L.sub.3 ; but not close enough to require overlapping or contact of any 
portion of the respective tabs T.sub.1 and T.sub.3. Additionally, when the 
T-beams 2 and 4 are thus bent, the tabs T.sub.2 and T.sub.4 are curvedly 
deformed in direct proportion to the radius or radii of curvature of the 
panel P and distance from the load bearing portions L.sub.2 and L.sub.4. 
Further discussion of the slot forms and tab positions will be detailed in 
reference to FIGS. 2 and 3 hereinafter. 
After the beam members 1-4 have been bent to the desired radius of 
curvature or arc, the oppositely directed pair of T-beams 1 and 2 are 
rigidly secured together, such as by clinches 13, drawn through the tab 
T.sub.1 and into the tab T.sub.2 as shown in FIG. 3, such that all points 
along the load bearing portions L.sub.1 and L.sub.2 are equidistant from 
each other, forming a pair of curvilinear parallel load bearing portions 
L.sub.1 and L.sub.2. Other means for securing the beam tabs together are 
contemplated, including a threaded bolt and mated nut arrangement, rivets, 
adhesives, and swedges between the tabs (where a portion of both tabs to 
be joined is punched through and folded over one of the tabs) to secure 
the beams in a parallel load bearing portion arrangement. The general 
overlapped tab arrangement, however secured, provides, in effect, a 
curvilinear I-beam configuration with all of the structural strength and 
rigidity inherent in such a structure. Additionally, the tabs T cover all 
but a small portion of the slots S, designated by the number 19 in FIG. 3, 
which inhibits vermin from entering and infesting the panel, while 
allowing sufficient controlled air convection though the panel to avoid 
bursting under elevated temperature gas-expansive conditions and limiting 
the convection and vapor condensation within the panel to provide optimal 
thermal insulating characteristics. The T-beams 3 and 4 are similarly 
secured together to form a pair of curvilinear parallel load bearing 
portions L.sub.3 and L.sub.4. 
End beam members, such as straight or linear I-beams 5 and 7 (FIG. 1) with 
load bearing portions L.sub.5a, L.sub.5b and L.sub.7a, L.sub.7b and spacer 
portions 6 and 8, respectively, are attached to the ends of the 
curvilinear beam members 1-4 to form a cylindrical frame, as by a bracket, 
such as L-bracket 9, and attached to the beams 5 and 7 by securing means, 
such as rivets 10. The non-riveted portion of the L-bracket 9 is then 
inserted into the grooves G of the pairs of beams 1-2 and 3-4. With the 
L-bracket 9 inserted into the grooves G a structurally rigid attachment is 
formed, as seen in FIGS. 1 and 4. lhe beams are attached such that the 
load bearing portions L.sub.1 and L.sub.3 are flush with L.sub.5a and 
L.sub.7a and the load bearing portions L.sub.2 and L.sub.4 are flush with 
L.sub.5b and L.sub.7b, respectively so that the frame of the panel 
comprises a pair of similarly curved I-beam members formed by the pairs of 
oppositely mounted T-beam members 1, 2 and 3, 4, joined at corresponding 
ends by straight I-beam members 5 and 7 to form a curved arc of a 
cylinder. Attachment in this manner provides in the panel frame a smooth 
upper load bearing surface formed by the edge strips L.sub.1, L.sub.3, 
L.sub.5a and L.sub.7a and a smooth lower load bearing surface formed by 
L.sub.2, L.sub.4 , L.sub.5b and L.sub.7b, respectively defining spaced 
coaxial cylindrical surfaces for receiving cover sheets. 
Adhesive or bonding material (schematically illustrated at A), such as 
epoxy resins, hot melt adhesives, or other customary permanent adhesives 
that will adhere or bond non-similar materials together, may be applied to 
the said edge strips that provide upper and lower or spaced coaxial load 
bearing surfaces of the frame noted above. Alternatively, the adhesive or 
bonding material may be applied to the load bearing surfaces of the beams 
prior to panel construction. 
After the adhesive or bonding material has been applied to the outer and 
inner frame edge strip load bearing surfaces of the beams, a pair of 
flexible covering sheets of material, such as fiberglass-resin sheets 11 
and 12, are adhered to the frame edge strips, as shown in FIG. 1, such 
that flexible sheet 11 contacts all portions of the outer frame edge strip 
load bearing surfaces L.sub.1, L.sub.3, L.sub.5a, and L.sub.7a and the 
flexible sheet 12 contacts all portions of the inner frame edges strip 
load bearing surfaces L.sub.2, L.sub.4, L.sub.5b and L.sub.7b. The sheet 
surfaces 11 and 12 are then coaxial parallel cylindrical outer and inner 
surface spaced by the panel frame. The flexible sheets 11 and 12 are 
preferably translucent or transparent sheets of limited thermal 
conductivity, capable of being bent and secured in curvilinear (including 
cylindrical) form while retaining structural integrity. Translucent sheets 
generally are used to insulate against heat loss where some thermal 
radiation is present and can penetrate the panel to provide a warming of 
the air within and on the other side of the panel, as a green house 
effect, while the limited conduction of heat through the panel provides an 
optimum barrier against heat loss through the panel. Prevention of gross 
circulation of external air can be achieved, where desired, by 
tape-sealing or otherwise blocking the slotted tab surfaces T along their 
surface at T', FIG. 1. Materials such as fiberglass-resin sheets or other 
plastic or resin composite sheets, plexiglass or plastic sheets are 
contemplated for the surfaces 11 and 12, though opaque materials may for 
some purposes also be acceptable. Additionally, it is desirable that the 
adhesive or bonding material be semi-flexible to absorb or compensate for 
the thermal and other stresses produced between the sheets 11 and 12 and 
the load bearing frame edge portions of the beams 1-4, 5 and 7. 
Alternatively, in some applications, the sheets 11 and 12 may be adhered to 
the load bearing surfaces by mechanical attachment, such as by screws, 
rivets, or nuts and bolts with or without a mastic material between the 
sheets and the load bearing portions of the beams. Such a mechanical 
attachment might be used where the flexible sheet material displays 
sufficient structural integrity and the environment for the panel P 
precludes the use of standard adhesives. 
Referring now to FIG. 2, a T-beam B, such as the beams 1 to 4, is normally 
composed of a load bearing cross portion of the T, designated L, connected 
intermediately at right angles to the longer portion of the T, shown as a 
spacer or fin material portion F. In accordance with the present 
invention, the fin material F is slotted at specified intervals and at 
right angles to the load bearing portion L of the T-beam B with one or 
more types of slots S to form a series of tabs T. The slots S can be cut, 
milled, ground or punched out of the fin material F, or the fin material F 
may be constructed with the slots S formed therewith. FIG. 2 
diagramatically and illustratively shows some of the different slot 
configurations that may be employed. The slots S can take many forms, but 
all commonly have a generally elongated configuration, that is that the 
length of the slot is greater than the width of the slot, where each slot 
has a first edge E.sub.1 and a second edge E.sub.2 that are joined near 
the load bearing portion L of the beam B by a vertex V. The preferred form 
of slot contemplated is the rounded V-slot, designated at S.sub.1, which 
has its converging edges E.sub.1 and E.sub.2 linearly approaching in 
direct proportion to the distance from the vertex V.sub.1, and a vertex 
V.sub.1 that is rounded to avoid the providing of a fracture point when 
the beam B is bent. Other slot types include the V-slot S.sub.2 with sharp 
vertex V.sub.2, the rectangular slot with flat termination V.sub.3 at 
S.sub.3, and the rounded vertex V.sub.4 of rectangular slot S.sub.4. 
After the slots and tabs are formed in the individual T-beams 1 to 4, the 
beams are bent to the preselected arc of curvature desired for the panel, 
as by pressing around a preformed mandril (not shown), such that the beam 
material permanently deforms to the shape of the mandril and assumes the 
preselected arc of curvature. The beam material must have sufficient 
ductability to allow reasonable bending without fracture and without loss 
of structural integrity. A T-bar or T-beam of structural aluminum, 
provides such a T-beam that is capable of being bent over a mandril by 
normal human strength without fracturing and that will hold the curved 
configuration. During the deformation process, the beams must be bent so 
as to produce a smooth arc of curvature that is free of kinks, sharp 
bends, cracks and fractures in the material. 
The size and shape of the tabs T and slots S are critical in the formation 
of a properly formed curvilinear beam. Using the structural aluminum 
T-beam and a rounded V-slot, as designated in FIG. 2 at S.sub.1, a tab of 
length approximately 1.834 inches measured from the edge furthest from the 
load bearing portion L of the beam B to the underside of the head portion 
of the beam B that includes the load bearing portion L, has been found 
most satisfactory. Additionally, the tab may have a thickness of 
approximately 0.040 inches and a width at its narrowest portion (furthest 
from the load bearing portion) based on the following chart: 
______________________________________ 
Radius of Curvature 
Tab Width 
(in inches) (in inches) 
______________________________________ 
18-30 1/2 
31-36 3/4 
37-72 1 
73-108 2 
109-132 3 
133-156 4 
157-216 5 
216+ 6 
______________________________________ 
The cross portion of the T-beam member serving as a load-bearing portion 
may be approximately 0.438 inches wide with a 0.041 inch thick head 
portion and a 0.094 inch recurved lip portions which form the grooves G, 
FIG. 1, more clearly shown in later-described FIGS. 4 and 5. When the 
panel is assembled, the slot is approximately 0.200 inches wide at the 
point furthest from the vertex and its edges taper in to approximately 
0.090 inches at the vertex, which is a semi-circular portion with a radius 
of curvature of approximately 0.045 inches. The vertex gains proximity to 
as close as approximately 0.229 inches from the load bearing surface L of 
the head of the T-beam. 
A panel constructed in accordance with this embodiment may be formed in any 
arc or series of arcs from a radius or radii of curvature of, for example, 
a foot and a half up to a straight curvilinear panel (radius infinite) and 
including complex curves, such as "S" curves and parabolas, by proper tab 
and slot sizes. Using differing materials and construction, curvilinear 
(including cylindrical) panels of smaller radii of curvature are possible 
in a similar manner. Additionally, a single beam may be formed into an arc 
portion of length greater than one-half of the arc of the circle, subject 
only to the mechanical requirements of the mandril or other curve forming 
operation and devices. 
The curved T-beam 1 is shown connected to the oppositely oriented parallel 
curved T-beam 2 in FIG. 3, wherein the beam 1 is the outer and the beam 2 
the inner of a composite curved I-beam formed by the pair of oppositely 
positioned T-beams 1 and 2. The slotted tab or long portions T.sub.1 of 
the T-beam 1 are shown overlapped with the slotted tab or long portions 
T.sub.2 of the T-beam 2, with their respective deformed slots S.sub.1 and 
S.sub.1 ' staggered along the arc and clinched at 13, preferably at 
alternative higher and lower spots, as shown. 
Referring now to FIGS. 4 and 5, FIG. 4 represents a standard tab-overlapped 
and clinched beam arrangement where the tabs T.sub.1 of the first beam 1 
are secured to the tabs T.sub.2 of the second oppositely oriented T-beam 2 
by a clinch 13, as previously described, with the respective slots 
staggered along the curve, as more particularly shown in FIG. 3. FIG. 5 
represents a similar arrangement, wherein the tabs T.sub.1 and T.sub.2 are 
deformed partially to surround a thermally insulating spacer material, 
such as a plastic foam strip 14. The tabs T.sub.1 and T.sub.2 are secured 
in a generally spaced parallel relationship and abutting the strip 14, by 
threaded bolt 15 and mated nut 16. Even though the arrangement of the 
beams, as in FIG. 4, in comparison with the size of the panel, with a 
large body of trapped, thermally insulating air, provides minimal thermal 
conductance through the panel, the use of an insulating spacer material, 
such as strip 14 shown in FIG. 5 reduces even further the thermal 
conductivity through the panel by the connected beam materials due to the 
thermally separated conductive material. 
Referring now to FIG. 6, the letter P again refers to the complex coaxial 
surface cylindrical insulating panel of the general type illustrated in 
FIG. 1, wherein like numbers designate like parts. To provide additional 
structural integrity to the panel P and better to support the plastic 
sheets 11 and 12 of FIG. 1, additional beam members may be intermediately 
secured to the original frame beams 1-4, 5 and 7. Specifically, 
intermediately disposed curvilinear beam members 19 and 21 may be secured 
to curvilinear beam members 20 and 22, respectively, in a manner similar 
to that previously described in connection with beams 1 and 2, and each 
beam member may be frictionally secured at its ends to the linear end beam 
members 5 and 7 by L-brackets 9, also as previously described. Preferably, 
the beams 1-4 and 19-22 are connected to the linear end beam members 5 and 
7 intermediate the frame in mutually parallel arrangement, such that the 
distance from one joined pair of beams 1-2, 3-4, 19-20, or 21-22 to its 
neighboring joined pair is the same for any pair of joined beams. For 
example, the distance between joined beams 19-20 and beams 21-22 is shown 
substantially the same as from beams 19-20 to beams 1-2. 
The curvilinear beams 1-4 and 19-22 are additionally supported by a series 
of straight or linear crossbars, such as I-beams 23, 25, 27, 29, 31 and 
33, in parallel relationship to the end beams 5 and 7 and joined at right 
angles to the curvilinear beams 1-4 and 19-22 such as by frictional 
engagement to the grooves G of the beams. Each I-beam 23, 25, 27, 29, 31 
and 33 has a first load bearing portion L.sub.23a, L.sub.25a, L.sub.27a, 
L.sub.29a, L.sub.31a, and L.sub.33a, respectively, and a second load 
bearing portion (not shown) separated by a spacer portion 24, 26, 28, 30, 
32 and 34 respectively. Each crossbar I-beam connects two joined pairs of 
curvilinear beam members along their length to provide greater structural 
rigidity. Therefore, when the plastic sheets (shown in FIG. 1 as 11 and 
12) are adhered to the panel P, the sheet 11 is adhered to the frame strip 
load bearing portions L.sub.1, L.sub.2, L.sub.5a, L.sub.7a, L.sub.19, 
L.sub.21, L.sub.23a, L.sub.25a, L.sub.17a, L.sub. 29a, L.sub.31a, and 
L.sub.33a and the sheet 12 is adhered to the load bearing portions 
L.sub.2, L.sub.4, L.sub.5b, L.sub.7b, the load bearing portions of beams 
20 and 22 and the opposite load bearing portion of the crossbar I-beams 
23, 25, 27, 29, 31 and 33. Such a configuration provides substantial 
internal support for the plastic sheets and further limits the thermal 
convection through the panel (controlled by the size and number of tab 
slots) and further inhibits the ability of pest infestation of the panel. 
Finally, as the panels are easily duplicated and have known, reproducable 
dimensions, since the beam 1 is bent around a pre-formed mandril before 
joining, frames can be produced to easily hold the finished panels. 
Additionally, since each panel has essentially flat edges that are at 
right angles to the arc of the preselected curve of the panel, multiple 
panels of the same radius of curvature can be joined without angled or 
wedged fittings. Alternatively, a joining clamp assembly may be used as 
described in my earlier U.S. Letters Pat. No. 4,129,973. 
Further modifications will also occur to those skilled in this art, and 
such are considered to fall within the spirit and scope of the invention 
as defined in the appended claims.