| 摘要 |
PROBLEM TO BE SOLVED: To provide a conduit switching device for an endoscope which has a good operability because of a small sliding resistance when a piston-like member is operated in a cylindrical member, and in addition, of which the annular seal member does not break, and which can be used extending to a long period of time. SOLUTION: The cross sectional shape of an external edge side part of the annular seal member 48 which comes into contact with the inner peripheral surface of the cylindrical member 31 is formed into a shape which protrudes to the outside into an approximate inverted V shape. At the same time, while a piston-like member 34 moves in the axial direction, the annular seal member 48 is elastically deformed by coming into contact with the internal wall surface of the cylindrical member 31. In this case, however, in order to make the elastic deformation amount smaller compared to when the piston-like member 34 is located at a standing-by position, the inner diametrical dimension of a part 31a of the cylindrical member 31 with which the annular seal member 48 comes into contact while the piston-like member 34 is moving is formed to be larger compared with the inner diametrical dimension of a part 31b of the cylindrical member 31 with which the annular seal member 48 comes into contact at the standing-by position. COPYRIGHT: (C)2004,JPO&NCIPI
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