PROBLEM TO BE SOLVED: To provide a pipe line changeover device for an endoscope, which includes a piston capable of being easily mounted, and which certainly prevents waste of gas inside a cylinder in a natural state.SOLUTION: A gas supply/water supply changeover device includes: a cylinder including a connection port connected with a supply source side pipe line, and a connection port connected with a nozzle side pipe line and a piston 81 fitted into the cylinder by insertion. The piston 81 includes: a piston body 82 having a first male thread 91m constituting a first fixing part 91 a first connection member 83 which has, at one end part, a first female thread 91f constituting the first fixing part 91 and screwed with the first male thread 91m, and at the other end part, a second male thread 92m constituting a second fixing part 92 and a second connection member 84 which has a second female thread 92 constituting the second fixing part 92 and screwed with the second male thread 92m of the first connection member 83. An inside diameter of the second female thread 92f is set to be an outside diameter of the first male thread 91m or less.COPYRIGHT: (C)2014,JPO&INPIT【課題】容易に組み付けを行えるピストンを備え、自然状態において確実にボンベ内のガスが浪費されることを防止した内視鏡用管路切換装置を提供する。【解決手段】送ガス送水切換装置は、供給源側管路が接続される接続口及びノズル側管路が接続される接続口を備えたシリンダーと、シリンダー内に嵌挿されるピストン81とを備え、ピストン81は、第1固定部91を構成する第1雄ねじ91mを有するピストン本体82と、第1雄ねじ91mが螺合する第1固定部91を構成する第1雌ねじ91fを一端部に有し、他端部に第2固定部92を構成する第2雄ねじ92mを有する第1の連結部材83と、第1の連結部材83の第2雄ねじ92mが螺合する第2固定部92を構成する第2雌ねじ92fを有する第2の連結部材84とを備え、第2の雌ねじ92fの内径を、第1の雄ねじ91mの外径以下に設定している。【選択図】図7
