Patent ID: 7789632

Claim:
Vacuum pumping method for reducing pressure in an enclosure, at least one primary pump and one secondary pump connected in series in a flow path of pumped gases and driven in same rotation direction by a first electric motor and a second electric motor, respectively, controlled by an electronic control module for modifying speeds of the two electric motors independently, the secondary pump having an inlet side and an outlet side, the inlet side of the secondary pump operatively connected to the enclosure, and the primary pump having an inlet side operatively connected to the outlet side of the secondary pump, comprising: at least one step, during reducing pressure in the enclosure, of progressively increasing the rotation speed of the secondary pump in accordance with a rotation speed variation law of the secondary pump; and at the same time progressively reducing the rotation speed of the primary pump in accordance with a rotation speed variation law of the primary pump; the progressively increasing of the rotation speed of the secondary pump being in accordance with a rotation speed variation law of the secondary pump that comprises a slowly rising first step followed by a fast rising second step followed by a moderately rising third step, and the progressively reducing of the rotation speed of the primary pump being in accordance with a rotation speed variation law of the primary pump that comprises a high-speed first step followed by a fast falling second step followed by a slowly falling third step.