Abstract: A dual-mode crawler unit for traversing a generally tubular target, the unit comprising means for effecting a hand-over-hand action along the target and also means for effecting a driven action along the target, the unit comprising two or more traversing units, the units being directly connected to each other by one or more linear actuators.

Abstract: A vehicle for traversing a surface such as for carrying out an inspection, survey or maintenance operation upon that surface comprises two bodies interconnected by means to move the bodies towards and away from each other, each of those bodies being supported upon a multiplicity of resilient bristles (13; 25; 32) extending from it, the bristles of each body being mounted in groups upon bristle-carrying members (10; 23; 31) each guided for movement towards and away from the body, and fluid pressure means (25; 22; 34) to effect the guided movement of the bristle-carrying members in at least one of those directions.

Abstract: A vehicle (1) for travelling along a conduit (2) having fluid flowing therein is described. The vehicle comprises a forward set of resilient bristles (12) and a rear set of bristles (18) which are adapted to move towards and away from the forward bristles (12). The forward bristles (12) engage the surface of the conduit (2) and apply a greater gripping force when they are moving towards the mar bristles (18) than when they are moving away from the rear bristles (18). Similarly, the rear bristles (18) apply a larger gripping force to the surface of the conduit (2) when they are moving away from the forward bristles (12) than when they are moving towards the forward bristles (12).

Abstract: A vehicle for traversing a surface, for example for carrying out an inspection, survey or maintenance operation upon that surface, includes two or more bodies interconnected by structure for moving the bodies towards and away from each other, each of the bodies being supported upon a multiplicity of resilient bristles extending from it. By relative movement of the bodies, the vehicle is able to traverse the surface, which may be flat or curved, for example the internal or external surface of a tubular conduit such as a tunnel, shaft or pipe.

Abstract: A vehicle, designed to move across an external curved surface such as that of a pipe or cable, for example to monitor the condition of the surface or enable the application of a treatment to the surface, comprises two generally hollow bodies, interconnected by means to move the bodies towards and away from each other, each body having generally parallel, generally flat resilient members each having a generally central aperture, which apertures are in general alignment.