| 摘要 |
Pairs of rotors (R1, R2, R3, R4, R5 and R6) driven rotationally by a motor (22) are disposed in the body (21) of a main pump (20) comprising a multistage Roots dry vacuum pump. A suction opening (23) communicating with the rotor chamber of the rotor R1 is provided in the upper wall portion at the left end of the body (21). A delivery section (24) communicating with the delivery side of the rotor chamber of rotor R6 on the final stage is coupled to an exhaust pipe (25) and is provided with a silencer (26) and further coupled to a check valve (28) through a pipe (27). The check valve (28) has its forward direction toward the atmospheric side. The delivery section (24), or a delivery section (24') at the side intermediate stage, is coupled to an auxiliary pump (30) having an exhaust capacity smaller than that of the main pump (20). When the motor (22) is driven, gas exhausted through rotation of the rotors (R1-R6) is carried sequentially to the downstream side from the rotor chambers and a vacuum processing chamber coupled to the suction opening (23) is exhausted. The delivery section (24) on the final stage is exhausted by driving the auxiliary pump (30), and the pressure is reduced. Consequently, the burden of the exhaust action on the rotor (R6) on the final stage or the rotor (R5) on the intermediate stage is lessened, and the power consumption of the motor (22) can be reduced significantly as compared with the prior art.
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