DRY VACUUM PUMP

摘要

A screw dry vacuum pump, wherein a shaft part (15b) of the rotor is provided with timing gears (16, 19) meshing with each other and a locking mechanism (17) for fixing the timing gears (16, 19) to the shaft part (15b), the shaft part (15b) and the toothed part (15a) being integrally cast of spheroidal graphite cast iron having an Ni content of 20 to 30 %. The toothed part (15a) is tapered from its center toward the discharge side at a taper ratio of 1/(20L), where L is the length of the toothed part (15a). A grinding surface is provided so that the diameter of the toothed part (15a) is decreased by 3/100 to 4/100 mm toward the discharge side from a position about 10 mm away from the center of the toothed part (15a) toward the suction side. N2 gas is fed into the casing. A discharge pipe (20) connecting a discharge port (7) to a scrubber (11) is a straight pipe without silencer.