Note: Descriptions are shown in the official language in which they were submitted.
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BRI~IDED AIRBEA118 AND METHOD OF MAKING THE 8ANE
BACKGROUND OF THE INVENTION
a. Field of Invention
This invention pertains to beams used in making variou~
structures such hangars, temporary shelters and the like, and
more particularly to air-inflated beams and a method of making
such airbeams.
b. Description of the Prior Art
Sometimes it is necessary to erect relatively temporary
structures in a short period of time. These structures may be
necessary for providing shelter to homeless people, military
personnel, for storing equipment during extreme weather
conditions, or for storing hazardous waste prior to disposal.
Such structures may also be used as hangars for aircraft or to
provide a protective dome for tennis courts or sport stadiums.
Typically such temporary structures are supported in three
different ways. One common method is to provide a substantially
semi-circular air impermeable membrane which is inflated and
supported by the internal air-pressure. This method can be
unsatisfactory because it makes use of noisy air pumps which must
be operated continuously. Moreover entrance and egress through
these structures can be effected only through air locks which are
slow and cumbersome to operate. In addition, economically it is
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~ unfeasible to provide these structures with air locks large
j enough to accommodate large equipment, such as for example a
truck or a helicopter and thus are unsuitable as hangars.
Another method of structural support frequently used consists
of frame work formed of metal bars, beams or pipes. ~ membrane
is then pulled over and secured to the frame. This method is
also unsatisfactory because it is expensive, time consuming and
can requires special skill and/or equipment to erect. Moveover
because of the weight of the frame components, it is difficult
and expensive to transport from one location to another.
A third method for supporting shelters also provides a frame
work, however its components consist of tubular pressurized
fabric members bent into curvilinear shapes. A membrane is
either integrally attached to, or pulled over and secured to the
pressurized fabric members. As a result these members require
substantial forces to bend them into curvilinear shapes. Moreover
if punctured they are prone to explosive depressurization
accompanied by catastrophic and rapid collapse of the structure.
OBJECTIVES AND SUMMARY OF THE INVENTION ~-;
In view of the above mentioned disadvantages of the prior art,
it is an objective of the present invention to provide an air
beam which is lightweight so that it is easy to transport form
location to location yet strong so that it can easily support a
~embrane.
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A further objective is to provide an airbeam which can be made
to any desired curvature without subjecting it to excessive
external forces.
Other objectives and advantages shall become apparent from the
following description. Briefly, an airbeam constructed in
accordance with this invention includes a bladder formed of a gas
impermeable material and surrounded by a sleeve. When the
bladder is inflated it takes on the shape of the sleeve to form a
straight or curvilinear airbeam. The sleeve is preferably made
of a braided fabric. Preferably the braided fabric is a
multilayer braided fabric with the layers being interlocked to
prevent delamination. A resin may be used to bond the fabric to
the bladder and to provide a protective coating to the fabric.
One method of making the airbeam consists of filling the -
tubular bladder with a solid granular material. The filled
bladder is bent to a preselected shape and then a vacuum pressure
is applied to the bladder to cause it collapse around the
granular material and form a solid mandrel. The fabric is
braided around this mandrel, after which the granular material is -
removed.
BRIEF DESCRIPTION OF THE DRAWINGS i~
Figure 1 shows somewhat schematically, a structure having
airbeams constructed in accordance with this invention; ~;
Figure 2 shows an elevational view of an air beam of Figure l;
Figures 3-8 shows the steps required to maXe the airbeam of
2 1 2 ~ 1 2 1
Figures 1 and 2; and
Figure 9 shows a cross-sectional view of the fabric using a
multilayered braiding system.
DETAILED DESCRIPTION OF THE INVENTION
Figure l shows an example of one type of temporary shelter lo
constructed of several airbeams 12, 12' forming a cross arch
frame work 11. Other significant types of frame works which can
be made with the subject airbeams include "arch and purling" and
"leaning arch". The frame work 11 supports a fabric 14 made of
canvas or other material satiable to provide roofing for the
temporary shelter 10 as discussed above. In Figure 1, airbeam 12
is curvilinear and is arranged amd constructed to extend
circumferentially from one side of the structure 10 to the other
with its ends being secured to the ground or other floor surface.
Beam 12' is also curvilinear and extends from the floor surface
until it intersects and is secured to beam 12 to form a crossed
arch framework. It should be understood that depending on the
size of the shelter 10 it supporting, the frame work 11 may be
constructed of several beams 12 and/or 12' as required. Since
the fabric 14 is supported by the frame work 11 of airbeams 12,
12', the shelter 10 can be provided with doors of various sizes
which have been omitted in the Figure for the sake of clarity.
Details of the airbeam 12 are shown in Figure 2. -Airbeam 12
includes a tubular bladder 20 made of a material impervious to
air. For example the bladder 20 may be made of a polymeric -
material. -At its ends, bladder 20 is provided with two end
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fittings 22, 24 arranged to provide an air-tight seal with the
bladder 20. Each fitting 22, 24 is provided with an air valve
26, 28 used to pump air into and out of the bladder 20 as
described more fully below. The fittings 22, 24 are provided
with threaded holes and the valves 26, 28 are screwed into these
holes, discussed more fully below. Preferably each end fitting
22, 24 has a conical section 30 and a substantially cylindrical
section 32. The bladder 20 is mounted peripherally on the
cylindrical section 32 of the end fittings as shown. End fitting
24 has a construction similar to end fitting 22 just described.
Disposed inside and extending through the bladder 20 is a
tether 40 with two ends. Each end of the tether 40 is attached
to the end fittings 22, 24 respectively. The function of the
tether is to hold onto the end fittings 22, 24 if the airbeam 12
is punctured to insure that the end fittings 22, 24 do not fly
off and cause damage.
A sleeve such as a fabric 42 is mounted on bladder 20
extending from one end fitting 22 to the other. As shown in the
drawings, the fabric 42 preferably overlaps the entire end
fittings to thereby provide an additional coupling means for
coupling the bladder 20 and end fittings 22, 24 together. The
fabric 42 and bladder 20 are secured to the fittings 22, 24 by
clamps 36, 38, 36', 38'. The fabric 42 is constructed and
arranged to defined a shape for the airbeam 12. For example in
Figures 1 and 2 the beam 12 is curvilinear with a preselected
radius of curvature. Alternatively, the airbeam may be a
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straight for use as a ridge or purlin.
Preferably the fabric 42 is a braided fabric because these
types of fabrics can be made in a tubular, seamless configuration
of with a curved longitudinal axis. A method of making the a
airbeam 12 is shown in Figures 3-8.
The first step, illustrated in Figure 3 is to provide bladder
20 in a desired length, thickness and outer diameter. The bladder
may be made, for example of a polymeric material by extrusion.
The tether 40 (which has been omitted from Figure 3 for the sake
of clarity) is positioned so that it extends longitudinally -
through the bladder 20. The bladder is then filled with a -
granular material such as a plurality of small plastic pellets 50
without substantially changing its generally tubular shape. The -
bladder ends are then pulled over the cylindrical section 32 of
shoulders of the end fittings 22, 24 and the bladder and end
fittings are temporarily coupled together by clamps 36, 38, 36',
38' (Figure 4~.
The bladder is now bent (Figure 5) so that its longitudinal
axis assumes a preselected curvilinear shape such as toroidal
shape, an elliptical shape and so forth as required. Of course
for straight airbeams the bladder is not bent. A vacuum source
52 is attached to valve 28 to reduce the pressure within the
bladder 20. As a result, the bladder 20 collapses over the
pellets 50 to form a solid curvilinear mandrel. Immediately ~ ~
prior to the depositing of the yarns about the mandrel, the outer -
surface 54 of bladder is preferably sprayed with an aqueous
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solution of resin from a resin reservoir 56 (Figure 5). A resin
useful for this purpose is available from Rohmtech of Malden,
Massachusetts under the name of RODAPUR 8055.
Next, the mandrel formed by the bladder 20 is positioned co-
axially with the axis of a braiding machine 58 and is fed intothe machine 58. As the mandrel advances through the braiding
machine 58, the machine braids a plurality of yarns 60 about the
mandrel to form the braided fabric 42. (Figure 6). In addition,
during this process in order to insure that the mandrel is
completely covered by fabric, clamps 36, 38, 36', 38' are removed
from the mandrel, without changing the low internal pressure of
the bladder. If necessary two clamps(not shown) much smaller
than clamps 36, 38 may be mounted on the ends of bladder 20 to
keep it secured to the end fittings while clamps 36, 38, 36', 38'
-15 are removed. These smaller clamps remain on the bladder 20 under
fabric 42. The resin solution sprayed on the mandrel from
reservoir 56 dries in the air and binds the inner yarns of the
fabric 42 to the mandrel. After the fabric 42 is braided onto
the mandrel, another resin solution is sprayed onto surface 54 of
the bladder to impregnate and bind the outer yards of the fabric
42 together and form a protective coating thereon. (Figure 7).
After the fabric 42 has been coated clamps 36, 38, 36', 38'
are again mounted to secure the fabric 42 and the bladder 20 to
the end fittings 22, 24. One of the valves, for example valve 28
is then opened to allow air to enter into the bladder 20. Next
the valve 28 is removed from the fitting 24 and the airbeam 12 is
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turned with the fitting 24 pointed downward to allow the pellets
50 to fall out (Figure 7).
Once the pellets 50 have been removed, the airbeams 12 can
be rolled up into a small package and transported to the site of
shelter 10. At the site, the bladder 20 is inflated through one
of the valves 26, 28 by air supply 74. (Figure 8). Once the
airbeam 12 is inflated, it is ready to be used to make a shelter
lO. As the airbeam 12 is inflated it takes on the shape of the
fabric 42.
The braiding process for making fabric 42 may be a
conventional two dimensional triaxial process. After braiding
the layers of the fabric may be impregnated more fully to insure
that the lager do not delaminate. However a three dimensional
multi-layer braiding system may also be in accordance with
commonly assigned co-pending application SN 551,266 filed -
July 12, 1990 and entitled SOLID BRAID STRUCTURE, now
. This system, shown in Figure g is
formed by simultaneously braiding several layers concentrically
about a common axis. Importantly, at regular intervals some of
the yarns of each layer are exchanged with the yarns of an
adjacent layer. More specifically, as shown in Figure 9, a
multi-layer interlocked braiding system 80 for forming fabric 42
includes a first layer 83 formed of yarns 82, 84 and a second
layer 87 formed of yarns 86, 88 and disposed adjacent to the
first layer 83. At regular intervais, such as 90 and 92, a yarn
from first layer 83 is exchanged with a yarn from the second
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layer 87. At other locations such as 94, 96 a yarn from layer 87
is exchanged with a yarn of a third layer 89 disposed adjacent to
layer 87. In the last layer (not shown); a similar yarn
traveling in the opposite direction of yarn 82 creates an
opposite border.
As a result, the several concentric layers are solidly
interlocked with each other to form a strong, substantially
homogeneous three dimensional fabric. Because the layers of the
fabric are inherently interlocked, these layers will not
delaminate and hence a bonding agent between each layer is not
required. Preferably the yarns used to make the fabric 42 are
high performance yarn such as a polyaramid such as Kevlar~.
Other suitable yarn materials include polyester, nylon, Spectra~,
fiberglass or carbon fibers. As these yarns are braided over the
solid curvilinear mandrel, the yarns in the longitudinal
direction inherently have different lengths to form the
curvilinear fabric. Using the method described above, airbeams
can be constructed having an outer diameter varying from 1" to
12", and a radius of curvature of the longitudinal axis varying
from 4' to 25'. Moreover these airbeams can be inflated up to
170 psi and when used to-make a shelter will support a standard
roofing membrane and additional loads disposed thereon such as
snow.
It has been found that the airbeam this produced, even if it
is punctured, it will release air at a relatively slow rate and
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I therefore it is made safer than pressurized fabrics previously
¦ used.
Obviously numerous modifications can be made to this
invention without departing from its scope as defined in the
appended claims.
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