Expanding and collapsing apparatus and methods of use

An expanding and collapsing apparatus comprising:

• a plurality of identical ring elements assembled together to form a ring structure around a longitudinal axis;
• and
• at least one set of structural elements extending longitudinally on the apparatus and operable to slide with respect to one another, wherein the sliding movement in a selected plane perpendicular to the longitudinal axis is tangential to a circle in the selected plane and concentric with the longitudinal axis;
• wherein the ring structure is operable to be moved between an expanded condition and a collapsed condition by movement of the plurality of identical ring elements, each identical element being in contact with an adjacent identical element in the expanded and collapsed conditions.

A method of expanding or collapsing an expanding and collapsing apparatus, the method comprising:

• providing a plurality of elements assembled together to form a ring structure around a longitudinal axis, wherein the plurality of elements comprises:
• at least one set of structural elements each having a first end and a second end and at least one set of ring elements each having first and second contact surfaces oriented on first and second planes, wherein the first and second planes intersect one another on a radial plane P which bisects the first and second planes between the centre of the ring and tangent points of an inner surface of the ring structure;
• moving the first ends of the structural elements in an axial direction, and moving the second ends of the structural elements in at least a radial direction;
• and moving at least one set of ring elements of the plurality of elements between the expanded and collapsed conditions by sliding them with respect to one another in a direction tangential to a circle concentric with the ring structure.