Patent ID: 6896490

Claim:
A vacuum apparatus, comprising: a plurality of vacuum containers each having a gas inlet and an exhaust outlet; a gas supply system for introducing a desired gas into each of the vacuum containers through the gas inlet; and an exhaust system for keeping each of the vacuum containers at a low pressure, the exhaust system including a plurality of initial stage vacuum pumps each connected to a respective corresponding exhaust outlet of its vacuum container, intermediate state vacuum pumps connected downstream of the initial stage vacuum pumps that lower back pressures of the initial stage vacuum pumps, and a latter stage vacuum pump connected downstream of the intermediate vacuum pumps; wherein an exhaust outlet pressure of the latter vacuum pump is substantially at atmospheric pressure, wherein the latter stage vacuum is constructed and arranged to exhaust gas from a plurality of the intermediate stage vacuum pumps, and wherein at least one of the plurality of the intermediate stage vacuum pumps is constructed and arranged to exhaust the gas from the plurality of the initial stage vacuum pumps.