US Patent 6863668 Articulation mechanism for medical devices

An improved articulating device for use with a medical insertion instrument comprising in part a first tube having a plurality of ribs defining a plurality of bending segments, a second tube axially disposed within the first tube, and means for transmitting an axial deflecting pull load. Such device has improved controlled for positioning an end of the device at a selected position within the body. The articulating device has a generally constant moment of inertia and a polar moment of inertia that generally decreases from its proximal to distal end.