| 摘要 |
PROBLEM TO BE SOLVED: To prevent a gas flow on the inlet duct side from leaking to an outlet duct through a by-pass. SOLUTION: The inlet duct 10 and the outlet duct 14 are connected by the by-pass duct 30 and poppet valves 44, 46 are provided at an inlet side opening 32 and an outlet side opening 34 of this by-pass duct 30 respectively. The respective poppet valves 44, 46 can be vertically moved by a common shaft 40. A space closed by the poppet valves 44, 46 when the shaft 40 is lowered to be a seal chamber 30A. An atmosphere introduction pipe 52 and a valve 50 are provided on this seal chamber 30A. The seal chamber 30A is sealed with external air by opening the valve 50 and closing the poppet valves 44, 46 at the time of normal driving. COPYRIGHT: (C)2004,JPO
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