PROBLEM TO BE SOLVED: To provide a ring-knot structure capable of performing stable deflection. SOLUTION: This is a nodal ring structure in which a plurality of nodal rings are sequentially adjacent to each other along the axial direction and are arranged so as to extend from a base end to a tip end. Each nodal ring 5 is formed in the side wall along the axial direction with a pair of mountain portions 52a arranged at positions substantially symmetrical with respect to the axial center, and a sway connecting the respective vertices of the mountain portions. Through holes 53a and 53b formed on one side of the moving center line L1 separated from each other and through holes 53c and 53d formed at positions substantially symmetrical with the through holes 53a and 53b with respect to the swing center line L1 are provided. The tip is engaged with each of the most advanced knots, and is inserted into four passages composed of the through holes 53a to 53d of each of the knots, and the base end reaches the base end of the knot structure 4 The wire part of the book was provided. [Selection diagram] FIG. 3B【課題】安定した偏向を行うことができる節輪構造体を提供すること。【解決手段】複数の節輪を軸心方向に沿って順次隣接して基端から先端にわたって延在するように配設してなる節輪構造体である。各節輪５は、軸心に対して互いに略対称な位置に配置された一対の山部５２ａと、側壁内に軸心方向に沿って形成されるとともに、山部のそれぞれの頂点を結ぶ揺動中心線Ｌ１の一側に互いに離間して形成された貫通孔５３ａ，５３ｂおよび揺動中心線Ｌ１に関して貫通孔５３ａ，５３ｂとそれぞれ略対称な位置に形成された貫通孔５３ｃ，５３ｄを備える。それぞれ最先端の節輪に先端部が係合され、複数の節輪の各貫通孔５３ａ～５３ｄにより構成される４つの通路に挿通され、基端部が節輪構造体の基端に至る４本のワイヤ部を設けた。【選択図】図３Ｂ
