External seal structure of vacuum valve

An external seal structure in a vacuum valve including:

• a valve body containing a valve part to control a fluid flowing in a flow passage;
• a cylinder cover connected to the valve body in abutting manner, the cylinder cover containing a drive part to give a drive force to the valve part;
• and a partition wall member including an upper end plate held between the valve body and the cylinder cover, the partition wall member being internally provided in the valve body to be extensible/contractible to separate between the drive part and the flow passage, the external seal structure including an annular seal member for main fluid placed between the upper end plate and the valve body to prevent the fluid flowing in the flow passage from leaking to atmosphere through an abutting section defined by the vale body and the cylinder cover connected in abutting manner,
• wherein the annular seal member for main fluid is made of perfluoroelastomer,
• a fluorinated annular seal member made of fluorinated resin is placed in a position between the upper end plate and the valve body and between the annular seal member for main fluid and the abutting section, and
• the valve body is provided with a leak port communicated with atmosphere, the leak port being communicated with between a seal point of the annular seal member for main fluid and a seal point of the fluorinated annular seal member.