PROBLEM TO BE SOLVED: To retain an insertion part inside a tube such as a digestive tract, while preventing the excessive-expansion of a cover for an endoscope, when a hole is opened on a balloon.SOLUTION: A propulsion mechanism 14a is constituted of first to fourth expansion/contraction units 28a-28d to be expanded in a diameter in the radial direction of the insertion part 16 by the pressurization from inside. The propulsion mechanism 14a is covered with a stain prevention cover 14b. The both ends of a cover body 65 in the stain prevention cover 14b are tied up with the use of piano wires 66, and a sealed internal space 68 is formed inside the cover. A pressure release valve 67 is arranged at the rear end of the cover body 65, which is opened when pressure inside the internal space 68 exceeds a prescribed threshold and is closed when the pressure becomes equal to or less than the threshold. The lower limit value of the threshold is set to a value for allowing the expanded stain prevention cover 14a to have pressure force against the inner wall of the digestive tract 72. The upper limit value of the threshold is set to a value smaller than a limit value at which the burst of the stain prevention cover 14b or damage to the inner wall occurs.COPYRIGHT: (C)2012,JPO&INPIT【課題】バルーンに穴があいたときに、内視鏡用カバーの過膨張を防止しつつ、挿入部を消化管等の管内に留める。【解決手段】推進機構14aを、内側からの加圧により挿入部16の径方向に拡径する第1~第4伸縮ユニット28a~28dから構成する。推進機構14aを汚れ防止カバー14bで覆う。汚れ防止カバー14bのカバー本体65の両端をピアノ線66で括って、カバー内側に密閉された内部空間68を形成する。カバー本体65の後端部に、内部空間68内の圧力が所定のしきい値を超えるときに開き、逆にしきい値以下のときに閉じる圧力解放バルブ67を設ける。しきい値の下限値を、膨張した汚れ防止カバー14bが消化管72の内壁に対して押圧力を有する程度の値に設定する。しきい値の上限値を、汚れ防止カバー14bの破裂あるいは内壁の損傷が発生する限界値よりも小さい値に設定する。【選択図】図13
