Patent ID: 7160081

Claim:
A vacuum pump comprising, in a common pump body ( 100 ), at least one molecular drag pump stage ( 5 ) in series in air-flow connection with at least one primary pump stage ( 9 ) of compatible speed, the molecular drag pump stage ( 5 ) having a molecular drag rotor ( 5 a ) co-operating with a molecular drag stator ( 5 b ) provided in the pump body ( 100 ), the primary pump stage ( 9 ) having a primary rotor ( 9 a ) co-operating with a primary stator ( 9 b ) provided in the pump body ( 100 ), the molecular drag rotor ( 5 a ) and the primary rotor ( 9 a ) being rotated by a common drive shaft ( 8 ) coupled to a motor ( 7 ), the pump being characterized in that: the molecular drag rotor ( 5 a ) includes a blind axial cavity ( 5 c ) that is open towards the downstream end of the pump body ( 100 ); the motor ( 7 ) is housed at least in part in said blind axial cavity ( 5 c ) of the molecular drag rotor ( 5 a ); the drive shaft ( 8 ) is coupled via its upstream end ( 8 a ) to the molecular drag rotor ( 5 a ); and the drive shaft ( 8 ) is coupled via its downstream portion ( 8 b ) to the primary rotor ( 9 a ); and wherein the primary rotor is a multistage regenerative rotor using viscous drag, comprising a disk comprising a transverse face carrying a series of concentric annular ribs each carrying individual radial blades, and the primary stator is a regenerative stator including a corresponding transverse face comprising a series of concentric annular grooves in which the individual radial blades of the regenerative rotor are engaged.