| 摘要 |
PURPOSE: A valve assembly is provided to prevent the intrusion of the contaminant into a mass flow controller by maintaining the pressure of the purge gas inside of a mass flow controller assembly at a positive pressure value. CONSTITUTION: The valve assembly(10) includes a poppet(50) capable of moving in the axial direction inside a passage of a main body member(20). The poppet(50) has an annular seal(54) capable of being engaged for sealing with a seal abutment part (shoulder part)(35) of the main body(20), and inhibits the flow of the fluid between a first end(21) and a second end(22) of the main body(20) in the case of engaging them with each other. A rotatable actuator(80) moves the poppet(50) in the axial direction so as to move the annular seal(54) from a position for engaging the annular seal(54) with the solder part(35) to a position for separating the annular seal(54) from the shoulder part(35). With this structure, flow of the fluid between the first and the second ends(21,22) of the main body(20) is allowed.
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