This invention relates to the field of pneumatic tubes used to support in an upright position flexible shelters usually made of a flexible membrane such as fabric, and in particular to an air beam which includes a plurality of individual inflatable beams, each of which having a nested sleeve construction so as to constrain the expansion under high pneumatic pressure of an internal resilient inner tube.
In the prior art, applicant is aware of applicant's own United States Patent Application, publication number US2008/0295417, published Dec. 4, 2008, for an Inflatable Beam Truss and Structure. In that patent application applicant describes a segmented inflatable beam truss which includes at least first, second, and third separate inflatable beams mounted to one another and having, respectively, first, second and third lengths and a substantially constant diameter amongst all of the three beams. Each beam includes an outer flexible substantially non-resilient sleeve along the entire length of the beam and an inner inflatable bladder extending substantially along and in the entire length of the sleeve. The applicant further teaches therein that, contrary to conventional wisdom which would require that pneumatic beams be increased in diameter as their length increases in order to support larger enclosures, that the use of a relatively narrow high aspect ratio pneumatic beam, where a plurality of such beams are mounted to one another, may be used to span relatively great distances if the beams are combined in side-by-side parallel array to form a single segmented beam truss. In jurisdictions allowing in corporation by reference, I hereby incorporate herein the aforesaid United States Patent Application Publication number US2008/0295417.
The drawback of that earlier design was that for use in high aspect ratio pneumatic beams I determined that the use of high pressurization was advantageous but caused the earlier design to fail. I have now found that using the airbeam of the present invention, for example as a twinned tube airbeam, or as an airbeam having a greater plurality of highly pressurized pneumatic tubes, that a greater stability may be achieved than I achieved in the past, where the airbeam resists twisting of the beam as it spans a long distance, for example forty-eight feet, and resists buckling at the vertex of the curvature when the airbeam is bent to provide a curved supporting member. Consequently, the earlier design had to be redesigned to allow for high pressurization for example pressurization exceeding 45-50 psi. As described below, the design of the present invention has been successfully tested at pressurization to 110 psi.
At high pressurization, I have found that the use of the earlier design, namely, the use of a single sleeve containing a resilient inflatable inner tube, failed along the stitching lines. Without the use of inverted sleeves and folded over, laterally spaced apart internal flat seams according to one aspect of the present invention, the expansion of the fabric at the seams allowed the resilient material, for example rubber, of the inflatable inner tube to push and expand into the spaces by bulging of the rubber between the stitching of the separating seams. I postulate that the bearing of the bulging rubber against the strands of the stitching increased the likelihood of failure along the seam.
The use of the highly pressurized airbeams according to the present invention was found to allow significant loading on the structure being supported by a plurality of such airbeams, when bent, so as to allowing forming for example of a dome or a quonset shape, when the ends of the bent airbeams are anchored to, for example, a floor panel or structure, and wherein the bending and the eventual domed or curved shape of the airbeam is governed by the curved shape of elongate fabric lumens formed in the flexible membrane of the domed structure.
Consequently, it is an object of the present invention, without intending to be limiting, to provide an airbeam capable of withstanding high pressurization and employing a plurality, for example, a pair of reinforced pneumatically inflatable beams mounted to one another so that the collective air beam is stabilized and resists twisting or buckling.
Other examples of pneumatically inflatable structures that I have designed may be found in for example, United States Patent Application Publication No. US2010/0175330 published Jul. 15, 2010, for an Inflatable Multi-Tube Structure, United States Patent Application Publication No. US2008/0210282, published Sep. 4, 2008, for an Inflatable Tent for Mounting into the Bed of a Pickup Truck, United States Patent Application Publication No. US2008/0313970, published Dec. 25, 2008, for an Inflatable Structure for Covering Sport Utility Vehicles, Boats and the Like, United States Patent Application Publication No. US2005/0197212, published Sep. 8, 2005, for an Inflatable Sport Ball Arresting Structure, United States Patent Application Publication No. US2007/0137113, published Jun. 21, 2007, for an Air Distribution System for Inflating Pneumatic Structures, United States Patent Application Publication No. US2008/0190472, published Aug. 14, 2008, for an Inflatable Structure for Covering Sport Utility Vehicles, Boats and the Like, United States Patent Application Publication No. US2009/0249701, published Oct. 8, 2009, for an Inflatable Quonset and Domed Structure and the Like, and U.S. Pat. No. 6,263,617, issued Jul. 24, 2001, for an Inflatable Self-Erecting Tent.
There is other prior art in the area of inflatable structures, for example, U.S. Pat. No. 6,260,306 which issued Jul. 17, 2001, to Swetish et al. for an Inflatable Shelter. Swetish et al. disclose an inflatable shelter having elongate inflatable tubes supported by the flexible membrane of the shelter so that a pair of the tubes form four legs supporting the membrane and wherein sleeves in the membrane define corresponding lumens for receiving the inflatable tubes. The lumens of the pair of sleeves are separated by at least one divider panel which extends substantially parallel to the pair of tubes.
In summary, one embodiment of the disclosed airbeam may be characterized in one aspect, as including a pair of resilient inner tubes, a pair of substantially non-resilient inner sleeves, a pair of substantially non-resilient middle sleeves, and a substantially non-resilient outer cover. When laid flat, each inner tube, each inner sleeve, each middle sleeve and the outer cover are substantially rectangular, each having a corresponding longitudinal dimension and a lateral dimension orthogonal to the longitudinal dimension. As used herein, the phrase substantially non-resilient means that the corresponding material or fabric expands slightly under tension, to an estimated five percent expansion when highly tensioned.
Each of the inner tubes' opposite ends are sealed, so that each inner tube is air-tight. The opposite ends of each inner tube are sealed by adhesive across the open ends and by being folded over along a fold-line adjacent the adhesive and the folded-over portion then bonded by further adhesive to an adjacent outer surface of the inner tube, adjacent the fold-line, so as to form a sealed folded-over end.
Each inner sleeve, each middle sleeve and the outer cover are each formed of an overlaid pair of substantially rectangular high aspect ratio sheets of flexible fabric sheeting. The overlaid pair of fabric sheeting has opposite ends and substantially linear side edges extending from, so as to extend between, the opposite ends. Each overlaid pair of fabric sheeting is stitched by side edge stitching along, and inset from each side edge, to form a flat side seam extending completely along each side edge and to form a corresponding cavity between the pair of side edge stitching. The cavity of the elongate sleeve so formed is bounded by the overlaid pair of fabric sheeting and the pair of side edge stitching. The stitching is also flexible. Once so formed, each overlaid and stitched pair of fabric sheeting is inverted, that is, turned inside-out, so that each flat side seam is disposed on the inside of the cavity of the sleeve and so that each flat side seam extends cantilevered inwardly into the cavity from the side edge stitching.
The outer cover further includes a substantially linear common seam, that is, linear when the sleeve is laid flat, which is parallel to the side edge stitching along each side edge. The linear common seam bisects the overlaid pair of fabric sheeting between the side edges. The linear common seam thereby forms a parallel, adjoining substantially identical pair of outer sleeves having the common seam therebetween. The pair of outer sleeves are thereby formed along the length of the outer cover.
One middle sleeve is nested within each outer sleeve of the pair of outer sleeves. One inner sleeve is nested within a corresponding middle sleeve in each outer sleeve. One inner tube is nested within a corresponding inner sleeve in each middle sleeve so as to form a parallel adjoining pair of inflatable beams adjoining along the common seam.
The longitudinal dimension of each inner sleeve, middle sleeve and the outer sleeve are substantially the same. The lateral dimension of the inner sleeve, middle sleeve and outer sleeve are, respectively, incrementally larger than one another so that the nesting of the inner, middle and outer sleeves is a snug nesting of one inside the other. Such snug, that is, tight, nesting causes each sandwiched flat side seam to be folded over against the adjacent sleeve walls. Thus the flat side seams of each side edge of the outer sleeve are folded over and compressed between each outer sleeve and a corresponding middle sleeve, and so that the flat side seams of each middle sleeve are folded over and are compressed between the corresponding middle sleeve and a corresponding inner sleeve. Each inner tube is journalled so as to be nested in a corresponding inner sleeve so that, when inflated, each inner tube compresses all of the flat side seams including the folded over side seams of each inner sleeve between each inner sleeve and the corresponding inner tube.
The nesting is arranged so that the side seams of the inner and middle sleeves are adjacent one another or overlap one another along their entire length and so that the side seams of the outer cover are adjacent or overlap the side seams of the middle sleeve. Whereby, upon inflation, the laterally outermost side seams of the inner sleeve, the middle sleeve and the outer cover are compressed substantially against one another so as to sandwich the side seam of the middle sleeve between the side seam of the inner sleeve and the side seam of the outer cover, thereby forming reinforced sidewalls on laterally opposite sides of the pair if inflatable beams when pressurized and inflated, the reinforced sidewalls herein alternatively referred to as reinforcing stringers.
Upon bending of the pair of inflatable beams when inflated to substantially 45 psi or more pressurization, the side seams lie substantially in three parallel planes which three parallel planes include the plane of curvature of the bending and of the airbeam. The two outermost planes of the three parallel planes include laterally outermost side seams of the pair of inflatable beams. The third plane is sandwiched between the two outermost planes and includes the common seam. When inflated to substantially 45 psi or more pressurization the side seams do not wrinkle but, rather, are compressed substantially flat, whereby buckling of the pair of inflatable beams at the vertex of the bend is inhibited during the bending of the airbeam. Although not intending to be limited to any particular theory of physical operation, applicant postulates that the combination of the three adjacent or overlapping side seams on each laterally outermost sidewall, when compressed at the high internal pressurization, act as stabilizing longitudinal stringers on each laterally opposite sidewall distributing the tension and compression forces due to bending along the side walls of the airbeam thereby inhibiting the stress relief mechanism of buckling formation. The stringers thus formed assist straightening the airbeam, inhibiting twisting or curvature of the airbeam out of the plane of bending. Further, the small (for example, five percent) expansion of each inflatable airbeam in the pair of airbeams, compress the airbeams against one another along the centrodial common seam, forming a further stabilizing wall along the common seam the tangent between the two tubes. This, it is postulated, further contributes to beam stability and resistance to buckling.
In the drawings where like reference numerals denote corresponding parts in each view:
a is the view of
a is a further enlarged view of
In the following descriptions of
a is, in plan view when laid flat, a first pair of overlaid fabric sheets for forming the inner sleeve.
b is, in plan view when laid flat, the inner sleeve formed by inverting the overlaid pair fabric sheets of
a is, in plan view when laid flat, a second pair of overlaid fabric sheets for forming the middle sleeve.
b is, in plan view when laid flat, the middle sleeve of
a is, in plan view, a third pair of fabric sheets when laid flat and overlaid on top of each other for forming the outer cover shown stitched along the side edges to form flat side seams.
b is, in plan view when laid flat, the outer cover once the initially stitched third pair of fabric sheets have been inverted and a longitudinally centroidal common seam stitched therealong.
a illustrates in plan view when laid flat one of the ends of the outer sleeve of
b is, in plan view when laid flat, the end of the outer sleeve of
a is an enlarged view of the folded-over end of the inner tube of
Pneumatic air beam 10 allows for pressurization to high air pressures in the order of 45-110 pounds per square inch (psi) while still allowing for bending of the airbeam. Airbeam 10 may thus provide a roof supporting beam in an inflatable structure having a plurality of such beams. It has been found that such high pressurization of the airbeams allows for tensioning of a fabric structure (not shown) supported by the airbeams sufficient to withstand for example a snow load or hundreds of pounds of weight suspended from the vertex of an airbeam supported structure supported by airbeams 10.
It is been found through experimentation by applicant that according to the construction of airbeam 10 set out herein, bending of airbeams 10 when highly pressurized, such as seen in
In a preferred embodiment, each pneumatic beam 10 includes a parallel snugly adjacent pair of inflatable beams 12, each substantially identical to the other and joined along a common sewn seam line 14 so as to bear one inflatable beam against the other when highly pressurized. Each beam 12 includes a rubber inner tube 16 which is slid into, so as to be journalled in and along its complete length within an inner sleeve 18, which itself is journalled in and fully along the length of a middle sleeve 20, which itself is journalled in and along the full length of an outer sleeve of outer cover 22.
Inner tube 16 is formed as a continuous hollow rubber sleeve which has a lateral dimension, when the tube is deflated and laid flat, of 6.4 inches (140 millimeters) and indicated by dimension “a” (in
Inner and middle sleeves 18 and 20 are substantially identical when laid flat as seen in
In the construction step from
Similarly, in the construction step from
Lastly, in the construction step from
Keeping in mind that the length of airbeam 10 may be in the order of twenty-four feet to thirty-five feet long, although this is not intended to be limiting, it will be appreciated that edge stitch lines 26 and common seam line 14 extends substantially the entire length of pneumatic beam 10. The exception is that common seam line 14 may not extend to the opposite ends of the airbeam in the region where each inflatable beam 12 of the pair of beams 12 making up airbeam 10 (in the twin tube embodiment) is tapered. Inflatable beams having more than two parallel, side-by-side beams may also be constructed by enlarging the width dimensions of the sheets and increasing the number of common seams 14 (for example two parallel spaced apart seams 14 for a three tube embodiment, and increasing the number of inner tubes 16 accordingly).
The tapering is done to snugly support end 16a of inner tube 16 within a tight collar 30 formed by inner sleeve 18, middle sleeve 20, and outer cover 22. With the exception of
As seen in the construction step between
Apertures 32 may then be formed through those sandwiched ends and flange 16b so that the opposite ends of beams 12 may be fastened using conventional fasteners (not shown) for example to the ground or a ground sheet 34 of a structure (not shown) for which airbeam 10 is providing structural support. Thus with the opposite ends of airbeams 10 fastened securely down to the ground, or to the opposite edges of a ground sheet 34, and with airbeam 10 constrained within a further sleeve or lumen within the structure being supported, inflation of each of beam 12 in airbeam 10 to its operating pressure of for example fifty-five psi (being for example one half of its maximum pressure of 110 psi), beam 12 will smoothly curve to form a smooth arch from one end to the other, being constrained within the sleeve of the structure, without buckling or cork-screwing so as to provide load support for the roof of, and structural rigidity to, the structure.
In one embodiment strips of backing material may be added along the stitching lines 24 and 26 front and back of each pair of overlaid sheets and stitched together with the sheets to provide extra material to hold the stitching to very high pressurization.
The nesting is arranged so that, as seen in
Upon bending of the pair of inflatable beams when inflated to substantially 45 psi or more pressurization, the side seams lie substantially in the three parallel planes P1, P2 and P3, which include the plane of curvature of the bending and of the airbeam. The two outermost planes P1 and P2 include the tight sandwich of the laterally outermost side seams (inner and middle sleeve side seams and the outer sleeve side seams) of the pair of inflatable beams. The third plane P3 is equidistant between the two laterally outermost planes P1 and P2 and includes the common seam 14. When inflated to substantially 45 psi or more pressurization the side seams, and hence the sidewalls, do not wrinkle but, rather, are compressed substantially flat hence forming a form of reinforced sidewall, whereby buckling of the pair of inflatable beams at the vertex of the bend is inhibited during the bending of the airbeam. Although not intending to be limited to any particular theory of physical operation, applicant postulates that the combination of the three adjacent or overlapping side seams of each reinforced sidewall when compressed at the high internal pressurization act as stabilizing longitudinal stringers on each laterally opposite sidewall, distributing the tension and compression forces due to bending along the side walls of the airbeam thereby inhibiting the stress relief mechanism of buckling formation. The longitudinal stringers thus formed by the reinforced sidewall assist in straightening the airbeam and inhibiting twisting or curvature of the airbeam out of the plane of bending. Further, the small (for example, five percent) expansion of each inflatable airbeam in the pair of airbeams, compress against one another along the centrodial common seam 14, forming a further stabilizing wall along the tangent on plane P3 between the two tubes as shown in
As seen in
As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CA11/00109 | 2/2/2011 | WO | 00 | 8/1/2013 |