BACKGROUND

The present invention relates to structural modules that can be selectively expanded into three-dimensional frameworks and collapsed into compact bundles of rod elements.

Structural modules capable of being manipulated between a collapsed, bundled condition and an expanded, locked condition presenting a rigid, three-dimensional space-frame are described in my prior U.S. Patents No. 4,473,986; No. 4,689,932; No. 4,761,929; and No. 4,838,003. In these patents, the structures have sufficient structural integrity in the expanded form due to stresses induced in the framework incidental to expansion to render the structures self-supporting either with or without any extraneous locking means, such as split-hub locking assemblies. These patents are each fully incorporated here by reference. Despite the advantages provided by the modules described in the foregoing patents, fabrication of large structures, such as aircraft or vehicle shelters, movable hospitals or storage depots, and the like, presents special concerns because the stresses induced in a large framework must be correspondingly large to render it self-supporting. Such stresses are generally so great that the safe erection of a large structure must occur in stages. Nevertheless, even staged erection presents problems in ordering the erection process and, since the total stress induced in the structure increases as it nears completion, in erecting the final few elements of a

large structure. Moreover, it is difficult to erect the framework without leaving the surface supporting it, e.g., by ^* using a crane.

Among its several features and advantages, the present invention permits the staged erection of large frameworks from the ground up, preferably using the frameworks including split-hub locking means described in the above-cited patents, by incorporating members having selectively adjustable lengths at predetermined locations in the framework.

Telescoping or otherwise changeable elements in rod frameworks are described in U.S. Patents No. 3,940,892 to Lindbergh; No. 3,973,370 to McAllister; No. 4,641,477 to Schleck; No. 4,655,022 to Natori; and Nos. 4,888,895 and 4,942,686 to Kemeny. The Lindbergh patent describes the erection of an aircraft enclosure by forming an arch through the extension of a piston in a hydraulic cylinder. The McAllister patent discloses the erection of a structure comprising a framework having extendable struts. Schleck teaches a modular rod/truss structure having chord and diagonal members comprising turnbuckles for length adjustments that permit arch construction. Natori teaches a framework including extendable truss beams that permit fabrication of a curved structure. The Kemeny patents teach a scissors-type framework in which telescoping members permit different curvatures to be developed.

None of the foregoing patents teaches a framework having an adjustable member as described in the present application that is selectively extensible and includes means for releasably locking the member at respective predetermined lengths to impart a predetermined shape to a structural framework in the expanded condition.

SUMMARY

In one aspect, the present invention provides a collapsible framework comprising a plurality of rod members, predetermined ones of which are selectively adjustable and self-locking. In its simplest form, the framework comprises a plurality of substantially half- octahedral forms joined by substantially tetrahedral forms, the bases of adjacent half-octahedrons being joined by common elements that form edges of the tetrahedrons and the peaks of predetermined adjacent half-octahedrons being joined by selectively adjustable elements that form other edges of the tetrahedrons.

Such a structural framework capable of being manipulated between a collapsed condition and an expanded, locked condition comprises a plurality of rod elements disposed generally in parallel with one another and in a bundle when said framework is in the collapsed condition, selected ones of the rod elements being extensible and including means for releasably locking the rod elements at respective predetermined lengths to impart a predetermined shape to the framework in the expanded condition. The framework further includes a plurality of hubs, each hub being disposed at a respective end of each of the plurality of rod elements and pivotally joining the rod elements so that the rod elements expand into a framework and certain of the hubs defining split-hub assemblies, and means for locking the hubs defining the split-hub assemblies together to maintain the framework in the expanded condition.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will be understood by reading the following detailed description in conjunction with the drawings in which: FIGS. 1A, IB, and 1C show the general arrangement of half-octahedral and tetrahedral forms in one embodiment of the present invention;

FIGS. 2A, 2B, and 2C show cross-sectional views of the central portions of a preferred embodiment of an extensible rod;

FIGS. 3 , 3B, and 3C show another embodiment including two extensible rods of a curved framework in the bundled, partially erected, and fully erect conditions, respectively; FIGS. 4A, 4B, and 4C show three exemplary structures;

FIGS. 5A-5G show the sequence of operations that could be used to raise the structure shown in FIG. 4C;

FIGS. 6A, 6B, and 6C show exemplary structures having different curvatures and horizontal extents; and

FIGS. 7A and 7B show an embodiment of split-hub assembly for use in the structures.

DETAILED DESCRIPTION

Referring now to the Figures in which like elements are identified by like reference numerals throughout, FIGS. 1A - 1C illustrate the general arrangement of substantially half-octahedral and substantially tetrahedral forms in one embodiment of the present invention. Rods or struts 10 - 13 are pivotally joined to respective hubs 14 - 17 and form the base of one half- octahedral module or body substantially in the manner shown in FIG. 3 of my prior U.S. Patents No. 4,473,986 and No. 4,761,929. One end of each of rods 19 - 22 is

pivotally joined to a peak hub 18, and the other ends of rods 19 and 20 are so joined to hubs 14 and 16, respectively. The other ends of rods 21 and 22 are pivotally connected to hubs 23 and 24, respectively, which form lockable split-hub assemblies or pairs with hubs 15 and 17, respectively. As described further below, peak hub 18 also forms one element of a split-hub configuration, and the configuration of the split-hub assemblies may be that disclosed in my prior patents that have been incorporated here by reference or the embodiment illustrated in FIGS. 7A and 7B.

It will be understood that the rods 10 - 13 are preferably of equal length; that the rods 19 - 22 are also of equal length; and that the lengths of the two groups of rods are preferably, although not necessarily, equal. In the collapsed, bundled condition, the three hubs 15, 17, and 18 are disposed at one end of the bundle; the hubs 14, 16, 23, and 24 are disposed at the bundle's other end; and the rods are disposed generally in parallel with one another.

As shown in FIG. 1A, for example, four substantially half-octahedral modules are combined by arranging for the adjacent modules to share one side of their bases. Additional peak and base hubs are provided corresponding to those above-described. The peak hubs of adjacent half-octahedral modules are joined by additional rods that have ends configured for forming split-hub assemblies, e.g., hubs 18 and 18-1 are joined by rod 26, and as noted in my earlier patents, the length of these additional rods determines the angle between the planes of adjacent modules.

It has been found that in erecting large structural frameworks, additional rods 26 having fixed, predetermined lengths result in structures that are difficult to handle and erect. Significant advantages are obtained by providing additional rods having

selectively adjustable lengths, but not just any type of adjustable rod will do. In accordance with one aspect of the present invention, an additional rod 27 is provided as shown in FIGS. 1A - 1C that is selectively extendable, is self-locking at a predetermined length, and includes an extension-limiting stop. When the adjustable rod 27 is set at a first extension having a length substantially equal to that of the other additional rods 26, as shown in FIG. 1A, a straight, or uncurved, framework is provided. Setting the adjustable rod 27 at a second, longer extension provides a curved framework as illustrated in FIG. IB, and setting the rod 27 to a third, shorter extension provides an oppositely curved framework as shown in FIG. 1C. As described in more detail below, preselecting the amount of extension provided by the adjustable rods 27 permits the erection of frameworks and structures having desired curvatures.

Referring now to FIGS. 2A - 2C, cross-sectional views of the central portions of a preferred embodiment of the adjustable rod 27 are shown for three extensions that may be considered as generally corresponding to FIGS. 1A - 1C. The rod 27 advantageously is formed of two telescoping tubes 271 and 272 made of a metal such as steel or aluminum and having specially shaped ends. As described above, the other ends of the rod 27 are pivotally joined to hubs for engaging in split-hub assemblies the peak hubs of adjacent half-octahedral bodies. The special shaping of the ends of the tubes 271 and 272 provides the above-described features needed for erecting large structural frameworks. It will be appreciated that the ends of the tubes 271 and 272 can be formed by conventional metal working processes, and for applications in which low weight is particularly desirable, the tubes could be formed of other materials, including plastics and composites. Whatever the material selected, it should have sufficient strength after

forming to prevent the tube 272 from being completely extracted from the tube 271.

The end of tube 271 preferably includes a depression 273, which may or may not extend completely around its circumference, that, in cooperation with a correspondingly dimensioned flared portion 274 on the end of tube 272, acts as an extension-limiting stop for the adjustable rod 27, thereby preventing the complete withdrawal of tube 272 from tube 271 as shown in FIG. 2B. It will also be appreciated that the inner diameter of the end of tube 271 is also preferably reduced to approach the outer diameter of the tube 272, thereby limiting the amount of axial misalignment of the tubes. It is believed that configuring the rod 27 so that the ratio of the distance between the depression 273 and the end of the tube 271 to the total extended length of the rod 27 is roughly 1:10 to 1:20 adequately limits axial misalignment c ^s the tubes. Of course, the particular value of the foregoing ratio is not critical, and suitable limitation of axial misalignment can be obtained for a wide range of lengths and diameters of the tubes.

One embodiment of a means for locking the adjustable rods at a predetermined extension is also shown in FIGS. 2A - 2C. Besides the flare 274, the end of tube 272 includes a spring locking member 275 that may be separately formed and disposed within the tube 274. As seen in the figures, the locking member 275 advantageously comprises a narrow strip of folded spring steel including a buttonhead 276 formed at one end. Such a device is commercially available as part no. A-130 from Valley Tool & Die Co., N. Royalton, Ohio. Buttonhead 276 projects through tu ≥. 272, which configuration, together with the resilience of member 275, obviates any need for fixedly attaching the member 275 to the tube's inner surface, for example by welding or soldering or other fastener. As shown in FIG. 2A, the buttonhead 276 slides

along the inner surface of tube 271 as the extension of rod 27 is adjusted. In FIG. 2B, the locking member's resilience allows the buttonhead 276 to ride over the depression 273 and permit full extension of the rod 27. In FIG. 2C, that same resilience causes the buttonhead 276 to snap through a correspondingly dimensioned aperture in tube 271, locking the tubes with respect to each other. It will be appreciated that the hubs on the ends of rod 27 limit rotation of the tubes 271 and 272 with respect to each other, thereby permitting reliable engagement of the locking mechanism, and by selecting the location of the aperture, the extension of the adjustable rod can be selected. It will be further appreciated that the locking mechanism can be disengaged and the extensible rod and structure collapsed by simply forcing the buttonhead 276 back through the aperture in the tube 271. In addition, the locking mechanism may include more than one buttonhead (and the tube a corresponding number of apertures therefor) for ensuring the mechanism's engagement.

FIGS. 3A - 3C show another embodiment including two adjustable rod members 27 of a curved framework in the bundled, partially erected, and fully erect conditions, respectively. The other rod members and hubs of the framework may advantageously be those described in my prior U.S. patents that have been incorporated by reference above or the hubs described herein. In the figures, six split-hub assemblies are forme.d by engaging predetermined ones of the hubs, indicated as fully blackened circles, with appropriate other hubs, indicated as open circles. The combined split-hub assemblies are indicated in FIG. 3C by the six partially blackened circles. The adjustable rods 27 render the framework curved in one direction (substantially from left to right in FIG. 3C) and straight in the orthogonal direction. Of course, it will be appreciated that rigid rod members 26

shown in FIG. 3C could be replaced by adjustable rods to obtain a framework curved in both directions. Moreover, it might be possible to replace the split-hub assemblies with fixed hubs by providing rod members (both rigid and adjustable) that were lockably hinged at suitable positions along their lengths.

Also shown in FIGS. 3A - 3C are tension cables 28 connecting diagonally opposed half-octahedral base hubs and indicated by the dotted lines. As tension members, the cables 28 provide additional strength and structural rigidity to the half-octahedrons. (For clarity, cables 28 are not illustrated in the other figures.) It will be appreciated that the rigidity provided by tension cables 28 can instead be provided by suitably strengthened hubs, but the cables have the advantage of being flexible, thereby facilitating collapse of the framework into a bundle. Of course, other forms of tension member could be provided, for example, hinged rod members. It will be appreciated that the number of substantially haIf-octahedral and tetrahedral forms in the frameworks shown in the above-described figures may be increased to obtain structures that are quite large. FIGS. 4A - 4C show three exemplary structures that could be used as aircraft or vehicle shelters or for other purposes. The collapsed and expanded structural frameworks are illustrated on the left sides of the figures, and the same frameworks covered by a flexible fabric or other shell material are illustrated on the right sides of the figures. Despite the size of these structures, one of the great advantages provided by the extensible rod element described above is that they can easily be constructed from the ground up. In addition, the present structures are pre-assembled and require no additional components, which could be misplaced. FIGS. 5A - 5G show the sequence of operations that could be used to raise the structure shown in FIG. 4C.

FIG. 5A shows the structural framework in a collapsed condition in which the lengths of four fixed rods 26 and ten extensible rods 27 are substantially equal and correspond generally to the condition illustrated in FIG. 2A as indicated by the A legend. FIG. 5B shows the framework expanded into a linear state such as that illustrated in FIG. 1A, and the lengths of the extensible members are still as in FIG. 5A. It will thus be appreciated that the split-hub assemblies can be formed with the structural framework conveniently located on the supporting surface and without the need for cranes or other equipment.

FIG. 5C shows the framework after the central portion has been raised from ground level. The central two extensible rods 27 are locked in position at lengths such as those illustrated in FIG. 2C as indicated by the C legend. The extensible rods 27 located at the transition from the raised to ground levels have extended lengths such as those illustrated in FIG. 2B as indicated by the B legend. As the central portion increases in height (FIG. 5D) , the lengths of those extensible members decrease until they are locked into place at lengths C as the adjacent rods 27 extend to length B. The sequence of extension and contraction continues (FIGS. 5E - 5G) until the structural framework is completely erected.

The importance of the combination of features provided by the extensible rods 27 should now be appreciated as permitting the structural framework to be erected from the ground up with a minimum of support equipment. Indeed, for sufficiently lightweight framework elements, the structure can be erected by hand without leaving the ground. The above-described self- actuating locking mechanisms enable the extensible rod elements to lock themselves in position without requiring additional effort, which might otherwise have required an elevated platform. The expandability (to length B) and

contractibility (to length C) of the rods 27 also facilitates ground-up erection by permitting a low-stress transition between raised and ground-level portions of the structure (see, e.g., FIG. 5B) . Furthermore, the extensible rod's extension-limiting stop prevents over- extending (and potentially disassembling) the telescoping rod elements.

It will be appreciated that the shape of the erected framework is determined, and thus can be selected, by the position of the extensible rods 27 as seen from the above-described figures and from FIGS. 6A - 6C. In FIG. 6A, a structure having a continuous curvature is obtained by including no rigid rod elements 26; FIGS. 6B and 6C illustrate how the height and horizontal extent of the erected structure can be selected by varying the number and position of extensible and rigid rod elements 27 and 26, respectively, as well as the amount of extension of the former.

FIGS. 7A and 7B show side and top views, respectively, of another embodiment of a lockable split- hub assembly that is preferred for use in large structural frameworks such as an aircraft hangar as a result of certain advantages over the split-hub designs disclosed in my prior U.S. patents. Referring to FIG. 7A, the split-hub assembly 180 comprises an upper hub

181, a lower hub 182 (shown shaded in FIGS. 7A and 7B) , and a hub locking member 183. FIG. 7A also shows a rod member 126 and a tension cable 128 pivotally joined to the upper hub 181 (only one rod member and one cable are shown for clarity) and a means 130 for attaching a fabric or other covering 132 to the assembly 180.

As seen from FIGS. 7A and 7B, hubs 181 and 182 are preferably sheet metal or other material and have substantially similar cruciform shapes that permit the two hubs to interlock when assembled, thereby preventing rotation of one relative to the other. The pivotable

connections of rod members 126 to the hubs 181 and 182 are conveniently established by pins 127 or similar means, and tension cables 128 may be conveniently pivotably attached to the hubs by lugs 129 engaging the same pins. The hubs preferably permit substantially unrestricted rotation of the rods about the pin axes to facilitate assembly and disassembly of the framework. A prototype of the hubs has been assembled from commercially available wall-shelving brackets comprising stamped sheet steel approximately 3/64-inch thick and 2 and 7/8-inches wide that were modified as illustrated in the figures and pivotally joined by pins to aluminum tubes of approximately 3/4-inch outside diameter and 1/16-inch diameter spun steel tension cables. Using such components, a 58-foot-long arched beam has been successfully constructed. It will thus be appreciated that pivotally joining the rods to the hubs in this way reduces the cost and complexity of these elements in comparison to the blade-type pivotable hub connections described in my prior U.S. patents. Besides the ease of making such connections, the adaptability of the framework is enhanced because larger rods may be used within the same space and the size of the rods may be changed with little difficulty. The hub locking mechanism 183 (seen most clearly in FIG. 7A) advantageously comprises a metal tube 184 for disposition through central holes in the hubs 181 and 182 and a resilient lock member 185 disposed within the tube 184. Member 185 preferably comprises a shaped spring steel member having opposed buttonheads 186 and opposed retaining ears 187 that protrude through correspondingly dimensioned apertures in the tube 184. The operation of member 185 is substantially similar to that of the rod locking mechanism 275 described above. It will be understood that the tube 184 may be permanently fastened to one or the other of the hubs, or alternatively the

outer surface of the tube 184 may have a circumferential lip 188 limiting its motion into the hubs and permitting free actuation of the buttonheads 186. In either event, the locking mechanism 183 releasably retains the hubs 181 and 182 in the interlocked position shown in FIG. 7A. In addition, it is preferable that the split-hub assembly 180 have the capability of releasably attaching a fabric or other covering 132 to the framework. Accordingly, it is advantageous that the tube 184 be dimensioned so that a means 130 for attaching the fabric may releasably engage the tube 184. Such a means 130 advantageously comprises a hub-like disc having an upstanding, bifurcated stub presenting headed tips 133 for releasably engaging the tube 184 substantially in the manner described in my U.S. Patent No. 4,473,986 that has been incorporated by reference.

The foregoing description is intended in all senses to be illustrative rather than restrictive. Other embodiments of the invention will suggest themselves to those of ordinary skill in the art, and those embodiments that fall within the spirit and scope of the following claims are intended to be included therein.