Polyhedron building system - Patent Review 5230196

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FIELD OF THE INVENTION

The present invention relates to a building system which includes the use of structural modules which form a shelter having a spherical surface, and more particularly to a self-supporting collapsible structure featuring structural modules having rigid locks and reinforcing cables.

BACKGROUND OF THE INVENTION

Building assemblies are known which have a foldable capability so that they may be erected where desired and, when necessary, folded up to a rather compact form for storage and/or transportation. These building structures are based upon column-like elements or rods which are used as basic construction units which function as stays. The links are interconnected with pivot joints, slip joints or other forms of movable interconnects, so that a collapsible, articulated structure is formed. A fabric covering is usually associated with the network of rods. An example of such a collapsible structure is shown in U.S. Pat. No. 3,185,164 which shows a structure including a plurality of rods joined by couplings into groups of three which are inter-related to form a generally hexagonal structural system. Another example of such a collapsible structure is shown in U.S. Pat. No. 3,710,806. Structures which utilize elements intended to maintain the rigidity of the structure are also known, as exemplified in U.S. Pat. No. 3,063,521.

The prior art is also generally cognizant of the use of collapsible frame structures for supporting tents or other outdoor shelters. Examples of collapsible frames for use in supporting such tents or outdoor structures are shown in U.S. Pat. No. 563,376; U.S. Pat. No. 927,738; U.S. Pat. No. 1,773,847; and U.S. Pat. No. 2,781,766. Such structures have varied widely in their ease of erection and storage, and are of varying structural strength.

Structures which are in the form of a dome or sphere are of interest because this shape achieves greater strength than other geometric shapes for the materials used. A dome structure also provides a great deal of interior space with a minimal amount of base area and building materials. However, spherical structures involve complex construction and difficult geometric relationships between the structural members. The complexity increases further when it is desired that the dome structure have a collapsible capability.

Attempts have been made to convert a plurality of flat planes into a spherical surface. Buckminster Fuller defined the spherical icosahedron (i.e., a polygon having 20 faces) by projecting a flat triangular grid onto the surface of a sphere. He utilized a 60 degree coordinate system, based on a triangular shape, which is very structurally stable. Fuller's icosahedron, as disclosed by U.S. Pat. No. 2,682,235, is known as a geodesic dome. However, Fuller's geodesic dome does not have a collapsible capability; rather, it is intended to be constructed by the user at the site of usage. For these reasons, the geodesic dome design is not always a practical structure.

In U.S. Pat. No. 3,968,808, issued July 13, 1976, Theodore Zeigler utilized Fuller's icosahedron in the form of a folding, self-locking structure. No new geometry was introduced. The patent discloses a self-supporting domed shelter constructed from a series of intermeshing pentagonal or hexagonal sections, each section being composed of crossed pairs of pivotally connected struts. The generally semi-spherical framework is made of elongate struts and hub means which are movable between a collapsed, bundled condition (in which the struts are closely bundled and in a generally parallel relationship) and an expanded condition of three-dimensional form. The structural framework as disclosed in this patent is self-supporting by virtue of self-locking action which results from the asymmetrical disposition of certain struts. The framework has zones of sliding connections between crossed struts, as for example at 110 in FIG. 1, which allows the structure to be collapsed.

In Zeigler's U.S. Pat. No. 4,026,313, each icosahedron face has alternate zones 18 and 20 of sliding and pivoted connections as shown in FIG. 1 of that patent. FIGS. 10-12A illustrate rectangular modules. U.S. Pat. Nos. 4,290,244 and 4,437,275 are divisions of U.S. Pat. No. 4,026,313 and are directed to structural modules.

As explained above, Buckminster Fuller converted a flat plane into a spherical surface or compound plane of several axes to form an icosahedron. Theodore Zeigler's later work, as shown for example in U.S. Pat. No. 4,689,932, converted a flat plane into a spherical surface, but in a different manner. Zeigler defined the octahedron shape, which allowed the ability to build long narrow structures or tall wide structures. An octahedron is a solid bounded by eight plane faces. With the octahedron based design, the struts which define the structural modules may be of equal length.

The octahedron design developed by Zeigler also introduced the 90-45 degree coordinate system. This design permits "stretchability" on three axes because each of the modules has the same edge lengths. That is, the controlled addition of modules permits the basic octahedron to be dimensionally increased in three mutually orthogonal directions: in height, in width and in length.

Zeigler's U.S. Pat. No. 4,689,932 employed the above octahedron concept to form a dome structure composed of square modules. This patent is incorporated by reference herein. The patent disclosed two types of modules: a "flat" module and a "transition" or cylindrical module. The circumscribing sides of all the modules are formed by crossed, pivotally connected struts.

With this design, the resulting building has a generally spherical shape which is substantially horizontal at the top of the structure and substantially vertical near the bottom of the structure, there being a curved portion therebetween formed by the transition modules. With this design, the corner portions of the building are left open if, for example, passageways are desired, as shown in FIGS. 1-3 of U.S. Pat. No. 4,689,932. As the size of the structure is increased, these open corner sections become progressively larger. The prior art does not address the problem of completely closing off the corner portions of the octahedron structures.

In regard to prior building designs, including the geodesic dome design and conventional structures such as frame tents, there are several general problems. If the structure is of the expandable/collapsible type, the structures are often difficult to erect, and require several workers, a significant amount of time, and special tools and equipment. The structures are also often complex in construction, having several different detachable parts and being relatively heavy and bulky in size. The non-uniformity of the size of the structural members also contributes to the overall complexity and cost of such structures. Many conventional structures, such as frame tents having a flat roof, are limited in their aesthetic appeal. As a result, the number of applications for which these structures are appropriate is limited.

The present invention addresses these and other problems associated with known collapsible support structures.

SUMMARY OF THE INVENTION

The present invention is a structural unit for a portable shelter framework. The structural unit is composed of elongated struts which are expandable into three-dimensional form and collapsible into a bundled form in which the struts are disposed in a closely spaced, generally parallel relation. According to one aspect of the invention, the inventive structural unit is a spherical module which, when expanded, defines inner and outer parallel faces, each of which are of a rhombus shape but which are of different sizes. The spherical module has two pairs of opposite side faces, each of the side face pairs defining non-parallel planes. Preferably, the module is circumscribed by crossed, pivotally connected struts of equal length. The spherical modules are combinable in an end-to-end relationship with other spherical modules or with cylindrical modules. A cylindrical module also has inner and outer parallel faces which each are of a rhombus shape, with the widths of the inner and outer faces being different and the lengths of the inner and outer faces being the same. That is, one pair of opposite side faces defines two parallel planes; and the other pair of side faces defines two non-parallel planes. The third type of module, the flat module, has parallel inner and outer rhombus shaped faces of the same size. As used herein, the term "rhombus" means a parallelogram with four equal sides and includes a parallelogram with either oblique angles or right angles.

In the preferred embodiment, hub means are provided to pivotally interconnect the struts, and the hub means have a radial cutout portion to accommodate angular distortion of the module's framework. The preferred embodiment of the structural unit also includes locking means for maintaining the modules in an expanded configuration. The locking means preferably is a releasable locking bar consisting of two members which are attached by a snap lock mechanism. According to another aspect of the invention, an expandable/collapsible structural framework for a portable shelter is disclosed. In the preferred embodiment, the structural framework is formed from a plurality of crossed, pivotally connected elongate struts which define a plurality of modules which are expandable to a three-dimensional form. A preferred embodiment of the structural framework includes a horizontal portion composed of at least one flat module, a plurality of vertical portions, each of which is composed of at least one flat module, a plurality of arch portions between the horizontal portion and vertical portions, each of the arch portions being composed of at least one cylindrical module, and a spherical triangle portion which is composed of at least one spherical module. Preferably, the structural framework is composed of struts of equal length and includes hub means which have angular distortion accommodation means, for example, a radial cutout portion which allows radial movement of the struts with respect to the hub. The preferred structural framework also includes cable members attached to struts or hubs which are organized in position by cable keeper members.

The inventive structural framework may also be formed with less than this number of structural portions. For example, the inventive shelter could be formed with only arch portions and spherical triangle portions; with vertical portions, arch portions and a spherical triangle portion; etc.

According to another aspect of the invention, a structural unit is disclosed which features a plurality of cables interconnected to cable retention means. The cable retention means are preferably cable keeper members, which consist of a strip of material interconnecting a corresponding cable with either a structural rod, another cable or a hub. Two types of cables are included with the present invention, periphery cables and diagonal cables. Various combinations of these cables, as well