Abstract:
Two substantially identical inflatable opposed frame elements, each consisting of a single unitary tube performed as by pleats or tucks causing the tube to assume a preestablished configuration when inflated, are connected at four points of intersection of the four tube ends with certain tube segments. Each inflatable element consists of an upwardly extending arch section, an upwardly extending brace section, and a substantially horizontal base section extending between and joining one foot of the arch section and the bottom of the brace section. The other foot of the arch section of each frame element intersects the base section of the other frame element, and the top of the brace section of each frame element intersects the top of the arch section of the other frame element.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     My invention relates to inflatable tents and similar temporary enclosures, and more particularly to structures of this type in which a sheltering cover is supported by an inflatable framework. 
     2. Prior Art 
     A wide range of inflatable structures appears in the prior art. At one end of this range, and most remote from the concepts of the present invention, are devices in which the tent sheathing or sheeting itself is inflatable, usually in a cellular arrangement. The prototypical art at this end of the range may be exemplified by U.S. Pat. No. 4,000,585 to Denaro, wherein an inflated cellular sheeting is supported by a conventional hardware frame--though with novel means of attachment to the ground. U.S. Pat. No. 3,540,170 to Flowers discloses a configuration in which substantially the entire sheathing is cellularly inflatable to form a self-standing frustoconical enclosure. 
     Near the center of the range of prior-art inflatable structures are enclosures in which the sheathing is unitary with spaced-apart inflatable frame cells. Typically the sheathing is of two-ply construction, in which the two plies are cemented or fused together everywhere except where the frame elements are desired; the unlaminated areas are simply inflated to form &#34;ribbing&#34;--frame elements. In U.S. Pat. No. 3,457,684 to Wood, this concept is shown embodied in such configurations as a pup-tent shape, a domed-vertical-cylinder or igloo shape, and a horizontal-half-cylinder or Quonset-hut shape. In U.S. Pat. No. 2,938,526 to Harrison et al., the same concept is shown embodied in a one-piece pyramid formed of several tetrahedral sections--with inflated rib cells along five of the six edges of each tetrahedron, and sheathing on two of the four sides of each tetrahedron; the entire pyramid may be adjusted in height by controlling (with a stretched rope or cable) the lateral distance between the bottom tips of the tetrahedra, which touch the ground. 
     At the other end of the range of prior-art devices, and most closely related to the present invention, are configurations in which the frame members are at least initially separate from the sheeting--though the sheeting may be strapped, glued or fused to the frame members subsequently. U.S. Pat. No. 3,899,853 to Wertman discloses sheeting having spaced-apart linear pockets, which accept simple inflatable cylindrical tubes to form parallel arched ribs of a Quonset-hut-shaped enclosure. U.S. Pat. No. 2,591,829 To Katzenmeyer et al. discloses frame segments united or jointed to produce an arched frame. A purported improvement to this is disclosed in U.S. Pat. No. 2,752,928 to Barker, wherein the frame members are preformed--that is, prearched--to prevent buckling and thus weakness of the frame. Barker shows parallel spaced tube arches with &#34;lodgepole&#34; tube sections connecting the tops of the arches. 
     The inflatable enclosure devices mentioned in the foregoing paragraphs mimic construction of hard-frame buildings. That is, they use the same structural elements and configurations as conventional structures made of wood or metal, merely substituting inflatable materials of construction for the conventional sheeting and framing materials. These prior devices thereby fail to realize the full potential for economy, sturdiness, ease of maintenance, safety, and speed of inflation and deflation which can be achieved through consideration of the basics of inflatable structures per se. 
     BRIEF SUMMARY OF THE INVENTION 
     My invention is a tent having a framework composed of two independently inflatable members which are assembled in a mutually opposed fashion. Each of the two members is a unitary, generally cylindrical tube which has two sealed ends. Typically the two frame members are provided with valves positioned to be in close proximity to one another when the structure is assembled, for ease in inflating and deflating the framework. Strapping or other attachment means are provided for attaching the members to one another, for securing the shelter cover to the frame, for securing the frame and shelter to the ground, and, if desired, for attaching equipment intended to be built into the finished structure or hung from the frame inside the finished structure. Aside from such valves and strapping or other attachment means, the inflatable members are substantially identical. 
     Each of the two frame members is preformed in a particular shape. I prefer to preform the frame members by providing tucks or pleats at certain points along the length of the inflatable tube. These tucks or pleats force the tube when inflated to form bends or elbows at the selected locations. Preferably the tubes are fabricated from long, relatively narrow sheets of fabric or plastic material. The tucks or pleats are formed by making transverse folds in the material at the desired positions and cementing or fusing them permanently in place. When the lateral edges of a sheet are bonded together and the ends sealed to produce an air-tight tubular casing, the shape and placement of the folds determine not only the degree but also the direction of bending at each elbow. To provide a smooth finish and strengthen and protect the tube in the region of these bends, the elbows are normally wrapped, or encased in an outer cover. 
     Each of the two frame members has an upwardly extending arch section which supports the tent sheeting at one end of the finished structure, and an upwardly extending brace section which helps to stabilize the arch section of the other member. The arch and brace sections of each member are connected by an intermediate base section. The base section extends between one foot of the arch section and the foot of the brace section. The base section defines one edge or side of the base of the enclosure and curves approximately halfway around the end of the base of the enclosure to a point approximately equidistant from both feet of the arch of the other frame member. 
     The free end of the brace section of each member meets and is secured to the central portion of the arch section of the other member. The free foot of the arch section of each member is secured to the base section of the other member, at a point opposite the other foot of that arch section. 
     In my preferred embodiment the arch section of each frame member is inclined upwardly away from the brace section of that frame member, so that in the finished frame the two arch sections lean away from each other. This configuration is advantageous because it tends to resist the tendency of the weight of the tent cover to pull the arch sections together (with resultant sagging of the cover). The weight of the tent-end material hanging downward over the ends of the arch sections torques the outward-leaning configuration of the arch sections further outward, stretching the cover across the top of the structure. Additionally, each frame member is capable of providing continuing support, preventing the complete collapse of the tent, in the event that the other member should become deflated. 
     Many, but not all, of the advantages of my invention result from the use of two independent inflatable frame members. Some of the advantages are present even if the frame is made with the four tube ends opened into and made integral with the mating tubing segments at the points where I prefer simply to secure them. Such a configuration, for example, retains the above-mentioned resistance against sagging of the tent cover. 
    
    
     The foregoing features and advantages will be more clearly understood by reference to the appended drawings, wherein: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view showing a tent embodying the subject invention, the concealed portions of the inflated frame being shown in phantom. 
     FIG. 2 is an isometric view of the tent frame of FIG. 1 with the sheeting removed. 
     FIG. 3 is a plan or top-orthographic view of the structure of FIG. 2; and FIG. 4 is an end-on elevation or orthographic view of the same structure. 
     FIG. 5 is an elevation, partly in cross-section, such as might be taken along the line 8--8 of FIG. 2, showing the relationship between the frame and the tent sheeting, in one embodiment of the invention; and FIG. 6 is an elevation showing in isometric projection the relationship between frame and sheeting in the same portion of the frame as represented in FIG. 5, but in an embodiment which is alternative to that of FIG. 5. 
     FIG. 7 is a cross-sectional view taken along the lines 7--7 of FIG. 6, further detailing the attachment of the sheeting to the frame. 
     FIG. 8 is an elevation, partly in cross-section, showing the securing of two frame members together, as may be taken along the lines 8--8 of FIG. 2, and also showing one convenient location for the valving of the two frame members. 
     FIG. 9 is a general elevation, partly cut away, showing the pleat or tuck method of forming elbows or corners in the tubing. 
     FIGS. 10 and 11 are end-on cross-sectional views of the frame tubing, showing two alternative constructions of the inflatable tube itself. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The general arrangement of the two substantially identical frame elements 1 and 2 and the sheeting 3 is shown in FIGS. 1 through 4. Typically the sheeting comprises upper portions 3a, with openable end-flap 3b, and flooring 3c if desired. The structure may be secured to the ground by pegs driven through grommeted loops 2v, 2x, 2y, 1z and corresponding others on the concealed side of the structure. 
     Frame member 1, preferably made of a single unitary tube having two ends 1k and 1m, and provided with conventional inflation/deflation valve 1w, forms straight sections 1a through 1j, separated by elbows 1m through 1u. Likewise frame member 2, having two ends 2k and 2m, and provided with inflation/deflation valve 2w, forms straight sections 2a through 2j, separated by elbows 2n through 2u. 
     Frame member 1 may be regarded as composed of an arch section 1a through 1e, and elbows 1n through 1q; a brace section 1j; and intervening base section 1f through 1h, and elbows 1s and 1t. The base section 1f-1s-1g-1t-1h is connected at elbow 1r to one foot 1e of the arch section 1a-1n-1b-1o-1c-1p-1d-1q-1e; and is connected at elbow 1u to the bottom of the brace section 1j. The term &#34;connected&#34; here refers to the abstraction of the connection of the conceptual arch, base and brace sections, whereas these sections are actually portions of a single continuous, unitary tube. 
     Likewise frame member 2 may be regarded as composed of an arch section 2a through 2e, and elbows 2n through 2q; a brace section 2j; and intervening base section 2f through 2h, and elbows 2s and 2t. The base section 2f-2s-2g-2t-2h is connected at elbow 2r to one foot 2e of the arch section 2a-2n-2b-2o-2c-2p-2d-2q-2e; and is connected at elbow 2u to the bottom of the brace section 2j. The term &#34;connected&#34; is here again used abstractly. 
     The free foot 1k of frame member 1 meets the base section 2f of the other frame member 2, and the free end 1m at the top of the brace section 1j of the frame member 1 meets the apex 2c of the other frame member 2. 
     Similarly, the free foot 2k of frame member 2 meets the base section 1f of the other frame member 1, and the free end 2m at the top of the brace section 2j of the frame member 2 meets the apex 1c of the other frame member 1. 
     The two frame members are secured to each other at the immediately aforementioned four points of meeting. A typical arrangement for securing the members together is shown in FIG. 8, which also incidentally shows the two valves 1w and 2w of the two frame members 1 and 2 respectively. The means for securing the frame members together shown here comprise two straps 6b, cemented, fused or otherwise permanently connected to the opposite sides of straight section 1a of frame member 1; another strap 6d passed around straight section 2f of frame member 2, and secured thereto if desired; and mating Velcro or equivalent strips 6c for securing the ends 6e of strap 6d to the ends of straps 6b. If preferred, snaps, buckles, blunt hooks, or any of a great variety of other attachment means may be substituted for the Velcro strips. 
     If desired the two valves 1w and 2w may be replaced by, or generally left open and augmented by, a single valve (not shown) connected to both inflation points in parallel. 
     As previously mentioned, certain of the advantages of my invention are retained in an alternative embodiment in which each of the four tubing ends 1k, 1m, 2k and 2m is opened into and fused or cemented to the mating tube section 2f, 2c, 1f or 1c, respectively. In this alternative embodiment the frame is a single integral unit having two arch sections, two brace sections and two base sections with a common, communicating interior. However, even in this case, for ease of inflation using standard fittings it could be preferable to provide either one or two valves, depending on the particular application involved; thus all of the appended drawings except FIG. 8 illustrate equally well the two-element-frame and the integral-frame embodiments. 
     The present invention would also of course encompass constructions in which tubing segments were opened into each other at certain of the four joints but not other(s). 
     As shown in FIG. 5 the side sheeting 3a and floor sheeting 3b may in fact be a unitary sheet wrapped around the base member 2f--and likewise at the other side of the structure base--with a zippered or other appropriate seam placed wherever preferred for convenience. 
     In the alternative, as shown in FIG. 6, the side sheeting 3a&#39; and floor sheeting 3b&#39; may be separate, and may be separately secured to the frame member 2f as by mating Velcro strips 4a, 4b, 4c, etc. 
     The either case the sheeting 3a or 3a&#39; may be generally secured to the vertical member 1a as illustrated in FIG. 7 by straps 5b spaced along the length of the vertical member 1a, the straps 5b being cemented, glued or fused as at 5a to the interior of the sheeting 3a or 3a&#39;, and being secured by mating Velcro strips 5c to straps 5d similarly fused, glued or cemented to the interior of the sheeting 3a, 3a&#39;. The sheeting is attached to the frame in this fashion merely to prevent excessive flapping or chafing. This attachment does not directly contribute structural stability. 
     Each corner or elbow is formed by taking a tuck or pleat in the material of the tubular frame element. The angle between the straight sections at each corner, and the orientation of that angle about the axis of the tubular element, are respectively controlled by the amount of material taken in the tuck and the orientation of the tuck about the axis, as will be apparent from consideration of FIG. 9, which for definiteness refers to the elbow 1n between straight sections 1a and 1b of frame element 1. As shown, the tube angles in the direction of the side of the tube where the tuck 7n is taken. The longer the tuck--that is, the greater the amount of material fused into the tuck--the sharper the angle between the straight sections. The elbow may be stabilized, protected and dressed by encasing it in wrapping 8n, which may be of resilient material such as synthetic rubber or may be a plastic sleeve shrunk into place over the elbow. 
     While all the features discussed with reference to FIGS. 5 through 9 are for definiteness related to specific portions 1a, 2f, 1b and 1n of the frame, it is to be understood that these references are intended only as exemplary of analogous frame locations where the same features come into play. 
     The frame elements 1 and 2 may be made, as shown in FIG. 10, of flat material 9 curved into a generally cylindrical shape with a fused, cemented or glued lap at 10; or in the alternative (not shown) may be made of extruded tubing. 
     The frame elements may be simple hollow tubing, or may as shown in FIG. 11 be &#34;bladdered,&#34; that is, formed with a plurality of smaller tubes such as 11a through 11h placed within outer casing 9&#39;, at least along portions of the frame length where the greatest strength is desired. 
     As one example of the finished product which may be constructed in accordance with my invention, the structure illustrated in FIGS. 1 through 4 may stand seven feet tall, with outer dimensions of the base approximately nine feet wide and fourteen feet long. (In addition, entrance areas can be extensible into work areas protected from the weather.) In such a structure, frame tubing six inches in diameter would be suitable. However, the design lends itself to increased or decreased size in all dimensions, with reasonable maintenance of proportionality. 
     Because of the simple frame construction, which is particularly economical for moderately short-run production, my invention produces relatively inexpensive though extremely sturdy and stable structures. 
     Its two main frame elements provide the benefits associated with interchangeable parts. 
     Because of the large-diameter tubing and simple construction, it is more rapidly inflatable and deflatable, and more completely deflatable--unless bladdered. The large-diameter tubes are more readily patched than small-diameter tubes appropriate for other inflatable-frame designs. 
     The structure&#39;s lightness aloft tends to resist wind deformation, unlike some prior-art inflatable-frame structures in which a concentration of elevated frame members occurs along the length of the enclosure. 
     The inflatable frame members may be made of urethane coated polyester, approximately 2 ounces per square yard polyester caseweight, with urethane exterior coating approximately 1 ounce per square yard and interior coating approximately 3 ounces per square yard, for a total weight of 6 ounces pe square yard. 
     In the alternative, an uncoated polyester fabric casing, of about 3 ounces per square yard, may be sewn into tubular shape with urethane film bladder, also 3 ounces per square yard, inside the casing. Such a bladder may be longitudinally multichambered., and preferably should be slightly larger in diameter (when unrestrained) than the casing. 
     The sheeting may be sailcloth. For waterproofing of the upper sections of the sheeting, where water can lie on the top of the structure, the sailcloth may be lightly coated with urethane or vinyl (though the latter tends to become tacky with age). The sheeting may be 3 to 3.5 ounces per square yard, including the waterproofing. Below the upper sections of the sheeting, depending on the intended application, the side sheeting may be water-repellant sailcloth, or may be water-repellant treated. 
     The flooring if separate from the top sheeting may be woven polyethylene, generally 4 ounces per square yard, sewn and waterproofed at its seams, or preferably impulse-welded. 
     The finished structure may be deflated, transported and reinflated without disassembly, the bottom sheeting serving as a pack. 
     If desired, additional large relief valves may be provided for the two frame elements respectively, to facilitate complete deflation, should check valves 1w, 2w not allow sufficiently rapid or complete deflation. 
     It will be understood that the foregoing examples and details have been chosen for illustrative purposes, and are not intended to limit the scope of my invention as it is defined by the following claims.