Patent ID: 7011491

Claim:
A friction vacuum pump comprising: a common cylindrical housing having an entrance opening and a discharge opening; a shaft rotatably mounted in the common housing and extending along an axis of rotation; a first pumping stage mounted to the rotor shaft and having an inlet adjacent the housing inlet, the first pumping stage including: a plurality of rows of stationary stator blades mounted on an element fixed to the housing, a plurality of rows of rotor blades carried by a rotating element arranged on the shaft for rotation around the axis of rotation, a longitudinal axis of the blades extending substantially axially, the rows of stator blades and the row of rotor blades being arranged concentrically with respect to the axis of rotation and meshing with each other, the rotor blades and the stator blades being canted to a radial direction such that as the rotating element rotates, a flow through the pump is directed radially from an outside inlet disposed adjacent the housing inlet to an inside outlet adjacent the shaft, a second pumping stage mounted on the shaft in the common housing adjacent the housing inlet, the second pumping stage including: an outer cylindrical stator with inwardly extending rows of stator blades, an inner cylindrical rotor with radially outward extending rows of rotor blades, the rows of stator blades and the rows of rotor blades being arranged concentrically with respect to the axis of rotation and meshing with each other, a longitudinal axis of the second stage stator and rotor blades extending in a substantially radial direction, the second stage rotor and stator blades being canted to the axial direction, such that as the rotor rotates, a flow through the second pumping stage is directed axially from an axially located inlet adjacent the casing inlet to an axially located outlet in communication with the casing outlet; the first pumping stage being arranged on the shaft at the inlet side of the second pumping stage; the common housing entrance opening being located between the first and second pumping stages.