Single stage root type-vacuum pump and vacuum fluid transport system employing the single stage root type-vacuum pump

摘要

A single stage root type vacuum pump has a pair of outside air introduction holes formed in the vicinity of a phantom line in an inner wall surface within a range between intersecting points, where the intermediate position that is located between the center of a driving side rotor shaft and the center of a driven side rotor shaft of three-lobe rotors intersects with the intersecting points at which internal circles located on the extended circumferences of the inner wall surface of the casing. The pair of outside air introduction holes formed in symmetrical positions into horizontally long slit shapes parallel to a width direction of the casing. Check valves are fitted to tip end portions of outside air introduction pipes which are respectively connected to outside air communication holes for preventing air from escaping at the time of reverse rotation of the three-lobe rotors.