MULTISTAGE VACUUM PUMP WITH IMPROVED EFFICIENCY

摘要

A vacuum pumping system (10) comprises a vacuum pump (12) having an outlet (16) for exhausting pumped gases from the pump, and at least one pumping stage (36c); means (40; 42a, 42b) for driving said at least one pumping stage (36c); and, downstream of the pump outlet, a valve (18) connected to the pump outlet (16) for receiving the exhaust gases therefrom, and an additional pumping stage (28), the valve being arranged to selectively convey the received exhaust gases towards and/or away from the additional pumping stage (28), wherein the driving means (40; 42a, 42b) is arranged to drive said additional stage.