Patent ID: 7793685

Claim:
An apparatus for establishing and controlling an appropriate low pressure gas mixture, including at least first and second gases, in a vacuum enclosure, the apparatus comprising: at least one secondary pump of a molecular, turbomolecular, or hybrid type; at least one primary pump adapted to deliver to atmospheric pressure; a first pipe having an inlet connected to an outlet of the vacuum enclosure and an outlet connected to a suction inlet of the secondary pump; an intermediate pipe having an inlet connected to a delivery outlet of the secondary pump and an outlet connected to a suction inlet of the primary pump; first control and adjustment means, disposed upstream from the at least one secondary pump, adapted to controlling and adjusting the total gas pressure of the mixture of gases in the vacuum enclosure as a function of a total pressure setpoint; second control and adjustment means distinct from the first control and adjustment means, disposed downstream from the secondary pump, for acting on the delivery pressure from the secondary pump in the range of pressures in which changes of the delivery pressure lead to variations in pumping capacity of the secondary pump with significant variations in the selective pumping speeds of different gases of the mixture and for acting on the delivery pressure in response to a delivery pressure setpoint so as to adapt the pumping capacity of the secondary pump selectively, thereby adjusting the pumping speeds of the different gases in the mixture of gases in the vacuum enclosure; and a control unit for controlling the second control and adjustment means in application of a specific program for adapting the pumping capacity of the secondary pump selectively to the various successive steps of a treatment process taking place in the vacuum enclosure, said control unit including means for generating a predetermined setpoint for said deliver pressure, at a specified step in the treatment process for which the second gas is to be evacuated from the vacuum chamber at a speed higher than the first gas is evacuated, and for providing the predetermined setpoint to the second control and adjustment means, said predetermined setpoint selected to cause the secondary pump to pump the first gas at a first selected speed and the second gas at a second selected speed greater than the first speed, thereby evacuating the second gas at a higher speed, as specified for the specified step in the treatment process, and partial pressure sensors determining partial pressure or one or more gases in the enclosure and operatively connected to said control unit, thereby controlling speed of removal of the first and second gases in the vacuum enclosure at the specified step in the treatment process by controlling the pumping speed of the secondary pump to favor pumping at least one of the gases, whereby said apparatus exercises control over both the overall gas pressure in the vacuum enclosure and the proportions of gases in the gaseous mixture of the vacuum enclosure.