Multistage discharge type rotary vacuum pump

摘要

A multistage discharge type rotary vacuum pump comprises a rotor rotably mounted within a cylinder chamber and dividing the cylinder chamber into first stage and second stage working chambers. A plurality of radially extending vanes are slidably mounted in the rotor in angularly spaced relation, and the vanes undergo radial sliding movement during rotation of the rotor such that the vane tips maintain sliding contact with the cylinder chamber. Each working chamber has an inlet port at the upstream side thereof for admitting exhaust gas evacuated from a confined space during use of the pump, and an outlet port at the downstream side thereof for discharging the exhaust gas which has been compressed in the working chamber in response to rotation of the rotor. The outlet port of the first stage working chamber communicates through a discharge valve with a storage chamber, and the storage chamber communicates through a pressure-responsive discharge valve with the inlet port of the second stage working chamber. The exhaust gas which is discharged from the first stage working chamber is stored in the storage chamber and whenever the gas pressure reaches a predetermined value, the pressure-responsive discharge valve opens to admit the compressed exhaust gas through the inlet port into the second stage working chamber. Such a construction enables miniaturization of the pump structure, a reduction in the driving force for rotationally driving the rotor, and an increased exhaust efficiency of the pump.