| 摘要 |
PURPOSE:To prevent a seal means for the casing from breaking owing to abrupt variation in external air pressure by providing a variable capacity mechanism composed of an expansible flexible member to part of an airtight wall. CONSTITUTION:A bellows 39 consisting of the expansible flexible member is provided to part of the wall 301 of the casing 30 where the optical position sensor device 31 is put. Even if an aircraft where the optical position sensor device 31 is mounted rises or falls abruptly to cause the external pressure of the casing 30 falls or rises abruptly, the bellows expands or contracts in conformity with variation in the external air pressure to balance the pressure in a storage chamber 40 with the external pressure at all times, thereby preventing the magnetic seal 36 from breaking. |
