Static structures (e.g. – buildings) – Striplike unit – reversibly flexible and rigid
Reexamination Certificate
1995-06-07
2001-07-10
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Striplike unit, reversibly flexible and rigid
C138S119000, C138S128000, C138S137000, C138S151000
Reexamination Certificate
active
06256938
ABSTRACT:
The present invention relates to an elongate hollow element arranged to be progressively flattened and wound into a compressed condition about one or more axes extending transversely relative to the longitudinal extent of the element.
It has long been suggested that self-supporting extensible tubes arranged to be stored in a compact coiled form would be useful for many applications. For example, U.S. Pat. No. 3,144,104 shows such a tube made of a resilient material such as spring steel or beryllium copper which is arranged to be wound onto a drum.
However, although there have been many proposals for such elements, currently no such elements are available in practice.
In seeking to make an element of this general kind it is necessary to make the material of the element thicker and more strongly prestressed towards its tubular form if it is to be sufficiently strong to resist bending loads when in its tubular form. However, the energy then required to flatten and wind-up the element becomes excessive. Because the elements are generally made of resilient metal, it has also been necessary to provide drums and the like to wind-up the element so that the user is not cut thereby. Furthermore, the potential energy stored by the coiled device is considerable and is a source of real potential danger. Thus, if the housing or other means holding the coil in position should break, this potential energy can be released explosively with consequent danger of serious injury. There is also a risk of injury when the element is being used normally as, when it is released from its coiled form, it may return to its tubular form at an explosive rate.
The present invention seeks to provide an elongate hollow element in which the disadvantages and risks outlined above are reduced.
According to the present invention there is provided an elongate hollow element arranged to be progressively flattened and wound into a compressed condition about one or more axes extending transversely relative to the longitudinal extent of the element, wherein said element comprises a substrate which is resilient and is biased towards said elongate hollow form, and means affixed to said substrate and arranged to oppose the bias of said substrate, and wherein the elongate hollow form and the compressed condition of said element are reversible.
As the means affixed to the substrate oppose the bias of the substrate, these means tend to favour the formation of the compressed condition of the element. By this means, the build-up of potential energy in the compressed condition is opposed, and may even be eliminated. Not only does this enable very strong elements to be safely stored in the coiled state, it also enables the safe release of the element to assume its elongate hollow form. Surprisingly, it has also been found that the invention enables such elements to be repeatedly easily wound and subsequently restored to their elongate hollow form.
It would be possible to wind the element into its compressed condition about a plurality of transverse axes, for example to form a concertina-like compact structure. However, for most applications it is preferred that the element be wound to form a coil having either a circular or a substantially rectangular shaped periphery.
Preferably, in its elongate hollow form, the element has sufficient rigidity to be self-supporting. Indeed, the element can be extended very readily from the compressed condition to the length required and the extended portion can be made to exhibit considerable structural rigidity.
In an embodiment, the means affixed to the substrate to oppose the bias of the substrate comprises a layer of a material which is subject to plastic deformation, for example to a layer of a plastics material laminated with the substrate. Thus, when the element is in its elongate hollow form, said layer can be arranged to be tensioned transversely of the element to oppose the curving of the element. In addition, winding of the element to its compressed condition deforms the plastics material to take up that position and thereby oppose the return of the material to its elongate hollow form.
Additionally or alternatively, the means affixed to the substrate may comprise prestressing means prestressed longitudinally of the element to favour formation of the compressed condition.
For example, the prestressing means may comprise at least one member extending longitudinally of the element which is under tension when the element is in its elongate hollow form, but which tension is arranged to be at least partially relieved when the element adopts its compressed condition. These prestressing means may comprise longitudinally extending prestressed fibres of glass or carbon. Such fibres may be embedded in a layer of plastics material laminated with said substrate.
Alternatively, the prestressing means may comprise longitudinally extending bands of prestressed rubber or plastics material.
Additionally and/or alternatively, means may be provided on the substrate prestressed transversely of the element to oppose curving of the flattened element into its elongate hollow form.
In an embodiment, said means opposing curving of the element may comprise members extending transversely of the element which are under tension when the element is in its elongate hollow form but whose tension is at least partially relieved when the element is flattened. For example, these transversely extending members maybe prestressed fibres, such as glass or carbon fibres. These fibres may similarly be embedded in a layer of plastics material laminated with said substrate.
Said transversely extending members may alternatively be elongate strips of resilient material, for example, of mesh or spring metal.
Said substrate may be a strip of spring metal, for example, spring steel or beryllium copper or may be a mesh of these materials. The use of a mesh substrate laminated to one or more plastic material layers is particularly favoured where the elongate hollow element is intended for repeated winding into and out of its compressed condition.
The cross-sectional shape of the elongate hollow element is generally curved to provide the necessary structural rigidity, but otherwise may be of any shape required. For example, the element may have a shallow arcuate form or it may be a closed tube of either circular or oval cross-section.
In one embodiment where the element is in the form of a longitudinally split tube, co-operable means may be provided on the adjacent longitudinally extending edges of the tube and arranged to releasably secure said edges together. In this way, the element in its elongate hollow form provides a tube.
In an embodiment the co-operable means comprise a longitudinally extending recess formed in one of the edges and a corresponding longitudinally extending projection on the other of said edges. Preferably, co-operating surfaces of said recess and projection are also formed with interengaging means.
In an embodiment, longitudinally extending formations, such as grooves or ribs, are formed on the element to increase its resistance to bending loads.
The present invention also extends to a portable structural element comprising a housing, and an elongate hollow element as defined above wound into its compressed condition and received within the housing.
Elongate elements of the invention may be used to make pipes, conduits, extensible arms, masts, tent supports, probes and aerials. In addition, means may be provided for driving the element from its compressed condition to its elongate hollow form and back again.
Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1
shows a perspective view of an embodiment of an elongate element of the invention illustrating the winding of the element to form a coil,
FIG. 2
shows a cross-section of the element of
FIG. 1
in its extended form,
FIG. 3
shows a cross-section of an alternative embodiment of an elongate element in its extended form,
FIG. 4
shows a partial longitudinal sec
Friedman Carl D.
Horton Yvonne M.
Nixon & Vanderhye PC
Rolatube Technology Limited
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