Apparatus for movably mounting a work head on a structure of circular cross-section.

摘要

An apparatus for movably mounting a work head (ll,l2) on a structure.of circular cross-section. The apparatus comprises an annulus defined by two or more members (l,2,3) which are engagable co-operably and movable between an open position which allows the annulus to be fitted onto the structure and a closed position in which the annulus surrounds the structure. The apparatus is located on the structure by locating means (6) comprising three or more support legs (6) mounted on the annulus at spaced circumferential locations. At least some of its legs (6) are movable in a radial direction relative to the annulus by actuating means to locate the annulus on the structure. Each supporting leg (6) is provided with drive means (8) which are controllable independently for moving the annulus along the structure in a plane normal to the axial centre line of the structure. The work head (ll,l2) is mounted on the annulus for circumferential movement with respect to the structure.