Patent ID: 7722332

Claim:
A composite dry vacuum pump comprising: a cylindrical housing formed with an intake on one side for inhaling an object substance and with an outlet on an opposing side for evacuating the object substance; a roots rotor embedded within the housing in communication with said intake; a screw rotor embedded within the housing and disposed proximate to the roots rotor, wherein said roots rotor and said screw rotor are mounted on a common shaft, wherein said shaft is rotatably mounted in the housing and sealed from the outside of the housing; and a driving motor mounted outside of the housing to rotate said roots rotor and said screw rotor via said shaft, wherein the housing defines a sump that temporarily contains said object substance, wherein said sump is disposed at an underside of said roots rotor and extends to at least a portion of an underside of said screw rotor, wherein a sump border is defined by the housing downstream of the outlet side of said roots rotor and upstream of the intake side of said screw rotor.