Abstract: A machine of the fluid entrainment or the positive displacement type, such as a compressor or a vacuum pump, in which injection of dry gas is effected in the discharge region of said machine or of one of its stages, wherein said injection is effected in a distributed manner over a surface.

Abstract: A two stage dry primary pump comprises, in a single common stator: a screw pump at its low pressure end; and a fluid viscous effect, single rotary screw gas exhaust pump at its high pressure end; with a link duct providing communication between the screw pump and the viscous effect, single rotary screw gas exhaust pump. The invention is applicable to vacuum pumps.

Abstract: The machine comprises first and second screw rotors (1, 2) supported by bearings (47) in a stator casing (3) which is provided with a suction inlet and a delivery outlet, the first rotor is driven by a motor (10) and the second rotor is driven by means of synchronizing gearing (11-12) situated in a first chamber (14) of the casing and located between the motor (10) and one of the ends of the rotors, the gearing (11-12) running in a lubricating fluid (15), the machine is characterized in that the cavity (30) of the casing containing the rotors (1-2) is separated from the first chamber (14) by a first wall (16) having the shafts (8, 13) of the rotors passing therethrough via seals (17-18), in that the shafts of the rotors at the opposite ends of the rotors to the ends having the gearing pass through a second wall (20) via seals (24-25), and in that the casing (3 ) includes, beyond the second wall (20), a second chamber (31) connected to the first chamber (14) by a main pipe (29) provided with pumping means (49)

Abstract: A method of starting series-coupled vacuum pumps comprising a primary pump (A) and at least one secondary pump (B) connected between the primary pump and an enclosure (E) in which a vacuum is to be established, the method consisting in starting the primary pump initially and subsequently starting the secondary pump when the suction pressure of the primary pump as reduced by rotation of the primary pump reaches an acceptable value, the method being characterized in that the pressure existing in the secondary pump is determined by using a physical magnitude related to the primary pump and following a law similar to the pressure law.