SCREW VACUUM PUMP
The invention relates to a screw vacuum pump comprising screw rotors (12, 14) disposed in a suction chamber (10). The screw rotors (12, 14) are each supported by means of two bearing elements (20) in the pump housing and comprise a ratio of rotor length (I) to rotor axis spacing (d) that is greater than 3.0. The screw rotors (12, 14) further comprise a variable pitch, at least 7 turns, and an integral compression ratio of at least 4.5. The pitch after half of the turns is less than twice the pitch on the pressure side rotor outlet (24).