Patent ID: 8246536

Claim:
A treatment tool insertion channel of an endoscope, which is arranged through an inside of an insertion part of an endoscope, the insertion part including a flexible tube and a bendable part linked with a distal end of the flexible tube, the treatment tool insertion channel comprising: a flexible inner tube; a spiral groove formed around the flexible inner tube, in an outer circumferential surface of the flexible inner tube, over an entire length of the bendable part and the flexible tube; at least one coil wound along a bottom of the spiral groove around the flexible inner tube; and a first filler and a second filler with which the spiral groove is filled, and wherein the flexible inner tube includes a first portion that includes a part inside the bendable part and a second portion at a proximal end side of the first portion, and a border portion connecting the first portion and the second portion, the first portion being configured more flexible than the second portion, wherein the second filler is harder than the first filler, the portion of the spiral groove extending the first portion being filled with the first filler, the portion of the spiral groove extending the second portion being filled with the second filler, and the portion of the spiral groove extending the border portion being filled with mixed filler which is a mixture of the first filler and the second filler, the mixed filler being a filler in which constituents of the first filler and second filler are blended together, the first filler and the second filler being made of a same type of material, between which a blending ratio is gradually changed such that a part of the border portion that is closer to the first portion is more flexible, and wherein the at least one coil is doubly wound along a bottom of the portion of the spiral groove extending the border portion, and wherein the border portion is located within a range of several millimeters to several centimeters between the first portion and the second portion, and flexibility thereof gradually varies at the border portion.