Bendable portion of an insertion tube of an endoscope and method of producing it

A bendable portion arranged proximate a distal end of an insertion tube of an endoscope, said bendable portion comprising:

• an outer bendable portion including a plurality of outer tube segments, each of said outer tube segments having a mantle and including connecting parts which cooperate with the connecting parts of an adjacent one of the plurality of outer tube segments for a hinge-type connection, the connecting parts of each of the plurality of outer tube segments axially protruding from faces of each outer tube segments, the connecting parts for each outer tube segment being located within and not exceeding the thickness of the mantle of the respective outer tube segment;
• an inner bendable portion-disposed within the outer bendable portion, the inner bendable portion including a plurality of inner tube segments, the plurality of inner tube segments numbering the same as the plurality of outer tube segments, each of said inner tube segments having a mantle and including connecting parts which cooperate with the connecting parts of an adjacent one of the plurality of inner tube segments for a direct hinge-type connection between the adjacent inner tube segments, the connecting parts of each of the plurality of inner tube segments axially protruding from faces of the inner tube segments, the connecting parts for each inner tube segment being located within and not exceeding the thickness of the mantle of the respective inner tube segments, said inner bendable portion including wherein four axially extending grooves provided on the outer peripheral surface of the inner bendable portion, the grooves being spaced circumferentially about the outer peripheral surface of the inner bendable portion at substantially 90°, each of said grooves having a control wire guided therein, the grooves of adjacent inner tube segments being held in alignment by the connecting parts between the inner tube segments,
• wherein the connecting parts of at least one of the plurality of inner tube segments being arranged in a pair, a first member of the pair being located on a first of the faces of the at least one of the plurality of inner tube segments, a second member of the pair being located on a second of the faces of the at least one of the plurality of inner tube segments, said first of the faces being opposite said second of the faces, the first member of the pair being circumferentially offset at substantially 90° relative to the second member of the pair.