Patent ID: 8371334

Claim:
A rotary switching valve comprising: a valve body formed with a chamber communication passage for flowing a main fluid and a vent communication passage for discharging the main fluid, the chamber communication passage and the vent communication passage being placed on facing side surfaces of the valve body, respectively; a cylindrical valve member rotatably held in the valve body and formed with a main passage for flowing the main fluid, the main passage having a process gas supply port formed on one end surface of the valve body, the cylindrical valve member being rotated to switch a connection of the main passage between the chamber communication passage and the vent communication passage; and a purge gas passage for passing purge gas in a clearance between the valve body and the cylindrical valve member, the purge gas passage including two purge gas passages, one of the two purge gas passages being positioned in between one end surface of the valve body and the chamber communication passage in an axial direction, the clearance being configured to receive the purge gas to prevent the main fluid from leaking out of the main passage; wherein the chamber communication passage and the vent communication passage are formed at a midpoint of the two purge gas passages.