Patent ID: 6776586
Filing Date: 2004-08-17
Classification: F04C

Abstract:
A multi-stage vacuum pump comprising: a housing in which a plurality of pumping chambers are formed, the pumping chambers being arranged in series and being in fluid communication with one another, one of the pumping chambers which is at one end of the series acting as an initial stage pumping chamber, another of the pumping chamber which is at the other end of the series acting as a final stage pumping chamber, the housing being provided with an inlet port for sucking a gas from a space to be evacuated into the initial stage pumping chamber, the housing being provided with an outlet port for exhausting the gas from the final stage pumping chamber; a Roots-type pump section occupying each of the pumping chambers; and first means for decreasing a temperature differential between the initial stage pumping chamber and the final stage pumping chamber, wherein the inlet port and the outlet port of the housing are placed near the initial stage pumping chamber, the first means is in the form of a passage connecting between the inlet port and the outlet port.