Flexible sheathing tube construction, and method for fabrication thereof

A flexible tube construction for an endoscopic insertion tube encasing at least one elongated flexible component of an endoscopic examination instrument within a hollow internal passage of the tube, comprising:

• a multi-layered wall including at least, from the side of the internal passage, an open helical coil structure formed of a flat metal strip having a predetermined width wound in a cylindrical shape in a predetermined open pitch so as to provide required flexibility in bending directions together with compressive strength, a protective mesh sleeve fitted on said helical coil structure, and an insulating outer coating layer formed on said protective mesh sleeve;
• and
• an inner coat layer of a resilient material formed on the inner periphery of said open helical coil structure to cover inner surfaces of helices of said metal strip completely, filling in gap spaces between open helices of said helical coil structure and keeping the at least one elongated flexible component in the internal passage out of contact with helices of said metal strip of said helical coil structure.