WO2008114092A1

WO2008114092A1 - All terrain collapsible tensegrity hammock stand

Info

Publication number: WO2008114092A1
Application number: PCT/IB2007/050933
Authority: WO
Inventors: Geoffrey Frankson
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-03-18
Filing date: 2007-03-18
Publication date: 2008-09-25
Anticipated expiration: 2009-09-18

Abstract

The present invention relates to the field of hammock support structures, but more particularly to those said structures which embrace the tensegrity hypothesis, having multifarious parts, with ease of assembly and disassembly, and lightweight in character. The tensegrity hammock assembly is a tensegrity structure consisting of a discontinuous set of compressed components inside a continuum of tensioned components - including the hammock itself. The counteracting forces of tension and compression result in a stable system that has the ability to yield increasingly to external pressure without breaking. As depicted in Fig. 1 the tensegrity hammock structure assembly of the present invention includes front and rear legs supporting uprights and spaced apart from each other in a longitudinal direction, each of said legs having left and right ends. The hammock of the present invention, hangs from and pulls upon the upper ends of two equidistant uprights, each consisting of struts and cords which are held together by opposing tension and compression. The weight of the occupant of the tensegrity hammock assembly is ultimately supported by the stiffness of the centre of an elevated horizontal strut (8), which connects the equidistant uprights. Since the shape of the structure is variable, the components can be of variable length, once cross-sectional symmetry is maintained. Since the struts are not rigidly attached to each other, the structure can be collapsed and folded to allow ease of transport. The only contact with the ground is at the four corners of the structure which allows usage on uneven surfaces. The lateral stability of the upper ends of the supports allows accessories to be attached, such as a sunshade or a tent. The central strut can be raised to alternatively provide support for a table instead of a hammock without compromising the stability of the structure.

Description

ALL TERRAIN COLLAPSIBLE TENSEGRITY HAMMOCK STAND BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to the field of hammock support structures, but more particularly to those said structures which embrace the tensegrity hypothesis, having multifarious parts, with ease of assembly and disassembly, lightweight in character and economically priced, thereby optimizing costs of manufacture, packaging, storage, handling and shipping.

2. Back ^vg&round Art

Traditionally, hammock structures are usually suspended from two spaced apart connector points. To secure a hammock connecting ring where there are no natural and properly spaced objects such as trees, walls or posts may be used. However, where the hammock structure's mobility is desirable, portable hammock supports or stands are employed.

As is evidenced in the prior art, one quite popular type of stand is a "sled" type structure, which employs two spaced apart rails with raised ends which each meet at a common point above ground. These ends contain rings or S hooks for securing the ends of the hammock.

Another well-known type of hammock stand is the "single rib" which includes a central rib pipe and two upstanding arms which are connected by a foot connector assembly. The foot connector assembly comprises a single four footed crosspiece, to which is welded a single "C" shaped bent tube, which is placed with a concave surface upwardly. The tube is welded at a plurality of joints, to the crosspiece to form the foot. Both ends of the tube are tapered with a smaller end and a somewhat enlarged medial section, so that the central rib pipe and the upstanding arm may fit thereon.

However a serious disadvantage of this said type of assembly is that the arm and a center rib pipe wedge so tightly on to the connector, that they cannot be removed from the connector after they are installed. Furthermore, the lift of the stand is very short and its inability to disassemble makes it an undesirable design. In addition, on uneven ground the straight cross-piece becomes unstable.

Additional prior art references include the following: US Patent # 5, 414, 873 - May 16, 1995 to Inventor Gary Wolf, in which a spring mechanism is employed albeit in the form of a hanger assembly for a similar purpose as stated previously.

US Patent # 4,691,394 - September 08, 1987, to Inventor Chi Goo Woo and in which the disclosure relates to a collapsible hammock which comprises light weight support members and a tensile strength wire member, for preventing the light weight support members from inwardly bending.

US Patent # 5,297,302 - March 29, 1994 to Inventor Bill R. Anderson also describes that the arm and base pipes telescopingly mounted onto the extension pipes. Of the known prior art tensegrity structures, the tension icosahedron has particular attributes that make it the most suitable for biologic musculoskeletal modeling (Levin, 1986). Icosahedral tensegrity structures are self-organizing space frames that are hierarchical and evolutionary (Kroto, 1988). They will build themselves, conforming to the laws of triangulation, close packing, and in biologic constructs, in accordance with Wolff's law.

The scapula, for example, fixed in space by the tension of its muscles, ligaments and fascial envelope, functions as the connecting link between the spine and the upper arm.

Wolff (1892) and Thompson (1965) state that the structure of the body is essentially a blueprint of the forces applied to these structures.

Consequently, there is definite need in the prior art for a tensegrity hammock support structure which overcomes the identifiable problems of contemporary commercially available units.

DISCLOSURE OF THE INVENTION

Therefore the main object of the present invention is to provide a tensegrity hammock structure assembly, with different operating principles and component parts from that of the prior art, for ease of assembly, disassembly, economical manufacturing, packaging, handling and transport costs.

For the present invention, an energetic form of the tensegrity hypothesis comes from mathematicians and is based on considerations of structural stability. According to this principle, all prestressed structures must assume an equilibrium configuration that minimizes the elastic energy stored in the structure. Insofar as this principle holds for all stress-supported structures, regardless of whether the prestress is balanced by internal compression elements, external objects, or a combination of the two, all pressure supported structures are tensegrity structures, such as is the present invention.

In classic continuum theory, by contrast, all solids possess intrinsic stiffness because the infinitesimal element develops local stresses that oppose local shear, even when the initial distending stress is zero. However, in stress supported structures, such as that of the present invention, stiffness and shape stability are maintained in the presence of prestress, even when an intrinsic stiffness is lacking entirely.

A secondary, but nonetheless important consideration concerning stress supported discrete structures is how the prestress is balanced. In some systems the prestress is balanced in its entirety by connections to the system boundary, with the prior art rope hammock assembly and the spider's web being good examples of such.

In other structures such as that of the present invention, though, most of the prestress is balanced by internal compression elements, sometimes called struts, that exist within the structure itself, with the posts of a pup tent and the inflating pressure of foam being other such good examples. Turgor pressure in a plant leaf and the inflating pressure of a lung are still other such suitable examples.

As they relate to the present invention, the main difference between these said dual types of stress- supported structures is that the forces balanced at each node, include only tensile forces in the former case, but both compressive and tensile forces in the latter case. Despite this distinction, both share the same central mechanism by which they develop restoring forces that oppose changes of shape, namely, the prestress.

Tensegrity structures, such as that of the present invention are fully triangulated and, therefore, there are no bending movements in these structures, just tension and compression and therefore significantly less loads to be reckoned with.

The present invention, as a tensegrity structure, is an omni-directional load distributor. The tension elements always remain in tension and the compression elements always remain in tension, no matter in what direction the load is applied. By contrast, this is not so in a column or a lever, which are rigidly oriented to resist a load from a specific direction. Therefore, because the loads in tensegrity structures such as that of the present invention are distributed all the time, each structural element can be lighter. Grant (1952) used a tension model to suspend the body, hammock like, when it hangs between gymnastic parallel bars. However, hammock like suspension is unidirectional. Turn the hammock or suspension bridge over and, not only does everything fall out of the hammock or off the roadbed, the hammock or roadbed also collapses.

A tensegrity hammock support structure, such as that of the present invention, can have one point of support coming from any direction and still maintain its structural integrity. Like a truss beam cantilevered off a wall, the internal elements remain solely in tension or compression with no movements at the joints. For example, when modeling a shoulder as a tensegrity structure the bones which "float" in the tension network of soft tissue are only being compressed. There are no movements at the joints because the structure is fully triangulated. In this model the shoulder becomes inherently stable and changes position only when one of the elements of the triangle is shortened or lengthened. Therefore, considerably less energy is needed to "stabilize" the joints.

BRIEF DESCRIPTION OF THE DRAWINGS

The above object and other features and advantages of the present invention will become more apparent by describing in detail, preferred embodiments thereof, with reference to the accompanying drawings of which:

FIG.1 is an isometric view of the tensegrity hammock structure assembly of the present invention.

FIG. 2 is a fragmentary exploded perspective view depicting one end of a tensegrity hammock structure assembly of the preferred embodiment.

FIG. 3 is an overhead perspective view of a preferred embodiment of a tensegrity hammock structure assembly of the present invention providing support for a sunshade. FIG. 4 is an isometric view of a preferred embodiment of a tensegrity hammock structure assembly of the present invention collapsed and folded for ease of transportation.

FIG. 5 is an isometric view of a preferred embodiment of a tensegrity hammock structure assembly of the present invention reset to be used as support for a table.

FIG. 6 is an overhead perspective view of a preferred embodiment of a tensegrity hammock structure assembly of the present invention providing support for a tent.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The word "tensegrity" has come to mean different things to different investigators. Remarkably, these differences have never been articulated and accordingly, have spawned at least a part of the controversy surrounding the hypothesis. In structural mechanics, for example, a clear distinction is made between tensegrity structures and other stress-supported structures.

Structures in which the prestress is balanced predominantly by internal struts are called tensegrity structures. This is referred to as the structural form of the hypothesis, which then identifies tensegrity as a subclass of the more general family of stress- supported discrete structures.

Among the family of discrete structures there is a special subclass called stress- supported structures. Within this subclass, discrete stress-bearing elements are postulated to carry preexisting tensile stresses even before an external load is applied; this initial state of tensile stress is called the prestress.

When an external load is applied, the structural elements must move relative to one another, changing orientation and spacing until a new equilibrium configuration is attained. Changes of orientation and spacing of the discrete elements represent the central mechanism by which restoring forces arise in stress- supported structures.

The tensegrity hammock structure assembly of the present invention includes front and rear legs spaced apart from each other in a longitudinal direction, each of said legs having left and right ends and is a tensegrity structure consisting of a discontinuous set of compressed components inside a continuum of tensioned components - including the hammock when occupied. The counteracting forces of tension and compression result in a stable system that has the ability to yield increasingly to external pressure without breaking.

The hammock of the present invention, hangs from and pulls upon the upper ends of two equidistant uprights, each consisting of struts and cords which are held together by opposing tension and compression, as outlined in the tensegrity theory of Richard Buckminster Fuller.

The struts of the present invention are not rigidly fastened together, but are held in position by the tension in the cords and if any component be removed, the said structure in its entirety would collapse. For the present invention, the weight of the occupant of the tensegrity hammock assembly is ultimately supported by the stiffness of the centre of the elevated horizontal strut, which connects the equidistant supports.

That said stiffness, in accordance with given tensegrity theory, is the net result of the opposing compression (of the upper side) and existent tension (in the lower side) of the elevated horizontal strut which stiffness must be sufficient to keep the strut above the surface, since contact affords a fulcrum for the pull of the hammock on the supports which then become unstable.

The shape of the structure is variable, depending on the lengths of the struts and cords; while the strength and stability depend on the tensional interactions between them. When assembled, the prestress in the system (particularly the tension in the hammock) maintains the structure. Remove any component and the entire structure collapses. Apply pressure (i.e. sit in the hammock) and the whole structure compresses with coupled, symmetrical movements that uniformly increase its stability.

The push-pull parts inherently triangulate and eliminate the torque in the opposing angles at the two ends of the horizontal bar. The stress created by the gravitational pull on the occupant of the hammock is directed to the centre of the bar.

Unlike other hammock stands, the mechanical stability of the structure of the present invention is a result of the way in which the structure balances and distributes stress rather than on the inherent strength of the individual components. The resistance to stress depends almost entirely on the stiffness of the elevated horizontal bar which ideally will yield up to the point of contact of the centre of the said bar with the ground (at which point the said structure becomes unstable, since a new leverage fulcrum is thereby introduced).

Since the tensile strength of the said structure does not depend on the parts but on the distribution of stress throughout the said structure, the components can be made of light material. Since the shape of the structure is variable, the components can be of variable length, once cross-sectional symmetry is maintained. Since the struts are not rigidly attached to each other, the structure can be collapsed and folded to allow ease of transport.

The tensegrity hammock assembly is a tensegrity structure consisting of a discontinuous set of compressed components inside a continuum of tensioned components - including the hammock itself. The counteracting forces of tension and compression result in a stable system that has the ability to yield increasingly to external pressure without breaking.

The pull of the hammock on the top of strut 1 is transmitted through struts 1, 2 and 3 downwards and inwards. Struts 6 and 7 then transmit this pull toward the centre of horizontal strut 8. This is countered by the tension in cords 1 and 2, which pull on the sides of struts 2 and 3, loop through the outer ends of struts 4 and 5, loop back through the tips of struts 2 and 3, and are tethered to the bases of struts 6 and 7. The opposing tension in the cords ensures that struts 2 and 3 maintain their vertical plane. The tension in cord 3, which runs from the conjoined tips of struts 2 and 3 to the supporting base of struts 6 and 7, transmits the pull of the hammock to strut 8. The support at the base of struts 6 and 7 carries the weight of the structure through struts 4 and 5 which are resting on the ground, with the tension in cord 3 maintaining the elevation of the base above the surface.

Strut 8 is raised off the surface on the inner ends of struts 4 and 5 at an angle to allow room for the belly of the hammock. The elevation of strut 8 is maintained by the tension in the cords which tighten as downward pressure is applied through the struts when the tensegrity hammock structure is occupied.

Cord 3 is actually an extension coil spring which, while maintaining the tension of the tensegrity structure, allows a degree of downward movement of struts 2 and 3 and consequently an inward movement of the upper end to which the hammock is tethered. The resulting oscillation enhances the relaxation experienced by the occupant of the hammock.

Unlike other prior art hammock structures, the mechanical stability of the present invention is a result of the way in which the structure balances and distributes stress rather than on the inherent strength of the individual components. The resistance to stress depends almost entirely on the stiffness of the elevated horizontal bar which ideally will yield up to the point of contact of the centre of the bar with the ground (at which point the whole system becomes unstable since a new leverage fulcrum is thereby introduced).

Since the tensile strength of the tensegrity hammock structure assembly does not depend on the parts but on the distribution of stress throughout the said structure of the present invention, the components can be made of light material. Since the shape of the structure is variable, the components can be of variable length, once cross- sectional symmetry is maintained, as demonstrated in Fig. 1 and 2. Since the components are not rigidly attached to each other, the structure can be collapsed and folded to allow ease of transport as demonstrated in Fig. 4.

Unlike other prior art hammock structures, the only contact with the ground is at the four corners of the structure which allows usage on uneven surfaces. Furthermore, the lateral stability of the upper ends of the supports due to the oposing tension in the cords allows accessories to be attached, such as the sunshade depicted in Fig. 3 and the tent in Fig. 6.

Unlike other prior art hammock support structures the central strut can be raised to alternatively provide support for a table instead of a hammock without compromising stability, as depicted in Fig. 5.

Claims

ALL TERRAIN COLLAPSIBLE TENSEGRITY HAMMOCK STANDWhat I claim is:

1. A configuration of a collapsible tensegrity structure hammock support assembly comprising:

front and rear legs of equal dimensions and equidistant from each other in a longitudinal direction, each of said legs having left and right extremities supporting uprights, and being in shape and form components of a tensegrity structure consisting of a discontinuous set of compressed components inside a continuum of tensioned components, including a hammock member;

wherein the improvement comprises:

a plurality of equidistant 'A' frame configured upright struts, said hammock member being suspended from a plurality of hooks and affixed detachably to the uppermost extremities thereof and of which said tensegrity support structure consists of a plurality of struts and cords held together by opposing forces of tension and compression;

a plurality of struts fastened releaseably, but held in position by latent forces of tension subsisting in a plurality of cords, while the weight of the occupant of the hammock member, by way of prestress transference, is redirected and ultimately supported by the tensile strength of the midpoint of a component tubular shaped, elevated, horizontal strut; and

a plurality of component parts which inherently triangulate and eliminate the torque in the opposing angles at either end of the elevated, tubular horizontal strut .

2. Said collapsible tensegrity structure hammock support assembly as claimed in claim 1, wherein a plurality of struts are made from material selected from the group consisting of plastic, metal, wood, or composite material.

3. Said collapsible tensegrity structure hammock support assembly as claimed in claims 1 and 2 wherein a plurality of cords utilized ostensibly for structural support, are made from material selected from the group consisting of string, nylon, chain or wire.

4. A collapsible tensegrity structure hammock support assembly, substantially as hereinbefore described and as claimed in claims 1, 2, and 3 hereof.