Pumping cells are formed between vanes 5 of a rotor 4 which is driven eccentrically in a pumping chamber 3 to draw in air from an inlet port 8 connected to a reservoir or directly to a consumer of vacuum and deliver air to an exhaust port 9. In addition to the inlet port 8 there is provided at least one auxiliary inlet port 10 or 10' which is connected to a separate reservoir or consumer of vacuum and it is arranged that this auxiliary inlet port 10 or 10' does not come into communication with a pumping cell 6 or 7 until communication has been discontinued between the first inlet port 8 and that cell. Connection between the auxiliary port 10 or 10' and the cell 6 or 7 is effected by means of a control slot 11 or recess 12 of the rotor which during pump operation periodically uncovers the auxiliary inlet port. A plurality of servo mechanisms may be operated by one single-action vacuum pump. IMAGE
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