Patent ID: 7980785

Claim:
A locking arrangement for selectively preventing displacement of a tubular support structure relative to an upstanding elongate support, the tubular support structure being concentrically situated around the upstanding elongate support and displaceable lengthways of the upstanding elongate support comprising a first structure selected from a single tapered internally projecting lug, or a recess, a plurality of such lugs or recesses arranged around a predetermined region of the support structure, wherein the elongate support is provided with a complementary shaped structure adapted for respective engagement with said first structure of the tubular support structure in such manner as positionally to locate the support structure with respect to the elongated support when at a lowermost limit of downward movement, and a rigid containment attached securely to an internal tubular surface of the tubular support structure and opening towards the outer surface of the upstanding elongate support, and wherein said containment houses a closely fitting inflatable container mounting a friction member for co-operation with said outer surface in such manner that the inflatable container is contained on three sides of the containment but can expand outwardly to press the friction member against the outer surface of the elongate support in order to exert a grip on the elongate support to prevent lengthways displacement and thereby maintain the support structure and any article/load carried thereby in a required position relative to the elongate support with sufficient force to prevent torsional yawing of the tubular support structure about the elongate support, and apparatus coupled to the tubular support structure for supporting an article/load with respect to the upstanding elongate support.