Clip for self-locking collapsible/expandable structures

A pair of adjacent collapsible, expandable, self-locking, self-supporting structures each comprising at least one section formed by a plurality of pairs of crossed rod elements pivotally joined in scissored fashion substantially midway between their ends, one rod element of each pair being pivotally joined at its opposite ends to two other rod elements of adjacent pairs of rod elements through associated hubs and the other rod element of said each pair being pivotally joined at its opposite ends to the remaining two rod elements of said adjacent pair of rod elements through associated hubs, whereby the pivotally connected ends of said pairs of rod elements lie and said hubs lie at corners of first and second similar polygons situated in spaced, parallel planes such that as the pairs of rod elements are scissored, the assembly is moved between a collapsed condition in which the first and second polygons are of contracted size and their planes are maximally spaced and an erected condition in which the first and second polygons are of expanded size and their planes are spaced relatively close, further rod means pivotally joined together and to the hubs at the corners of said polygons for self-locking said section in said erected condition, said further rod means comprising a first set of rod elements pivotally joined together at the plan view geometric center of said first polygon and extending therefrom to pivotally connect to hubs at the corners of said first polygon, said rod elements of said first set being of lengths such that they lie essentially in a common plane containing said hubs and corners of said first polygon when said first polygon has expanded to a maximum size, said further rod means also including a second set of rod elements pivotally joined at hubs at corners of said second polygon and to intermediate portions of corresponding rod elements of said first set so that said rod elements of the second set can not be essentially in a common plane containing the corners and hubs of said second polygon even when the section is in erected condition, said rod elements of said second set being of lengths between their corner/hub-connected ends and their pivotal connections to the corresponding rod elements of said first set such that as said polygons are expanded, the rod elements of said first and second sets thereof interact to place all of the rod elements of said assembly under cumulative self-locking stress in said erected condition of said section, at least one hub of each section being adjacent each other, means for releasably securing said at least one hub of each section to each other, and said releasable securing means including at least two stems with each stem being interlockingly received in an associated opening of said last-mentioned hubs.