A self-driving and self-locking device for traversing the inner walls of channels enclosed on all sides, or for traversing the outer casing of structures with a substantially constant cross-section over their lengths, and for affixing itself thereon, which includes a frame, propulsive elements disposed...http://www.google.de/patents/US4085808?utm_source=gb-gplus-sharePatent US4085808 - Self-driving and self-locking device for traversing channels and elongated structures
