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Image Number 4 for United States Patent #4539786.
A structure capable of being expanded and retracted. The structure includes a pair of cells each including a plurality of leg elements which are pivotally joined at one end to form an apex point and which are pivotally joined at their opposite ends from the apex point connection to the corresponding leg element from the other cell to form a plurality of common base points. The structure also includes a plurality of hinged elements connected between adjacent common base points to thereby form a common base and the hinged elements each have a pair of sections that are connected at a hinge point approximately midway between the adjacent common base points to which the other end of each section is connected. The structure further includes an actuator means having its ends pivotally attached to the apex points and a means associated with the actuator means for biasing the apex points to which the actuator means is attached towards and away from each other whereby the leg elements pivot about the apex points and the base points, the sections of the hinged elements pivot about the base points and the hinge points to thereby expand or retract the structure, respectively.
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