Patent ID: 7472662

Claim:
A vacuum pump, comprising: a housing having a housing base and a housing cover defining a volume therebetween and a central inlet through said housing cover; an impeller arranged within said housing, said impeller having a central opening in fluid communication with said central inlet; wherein said housing base comprises a shaft opening for receiving an output shaft having a threaded end portion for penetrating said shaft opening; wherein said impeller comprises a central aperture for receiving said output shaft, said impeller comprising a shoulder within said central aperture, and a cap, said cap having a head portion and a threaded shank portion that is screwed into a threaded region of said central aperture; wherein said impeller is securable to said output shaft by a nut tightenable on said threaded end portion, said nut bearing against said shoulder when tightened on said threaded end portion, and wherein said threaded shank portion is threaded into said threaded region of said central aperture to a first threaded depth, and wherein when said nut is removed, said threaded shank portion can be threaded into said threaded region of said central aperture to a second threaded depth, deeper than said first threaded depth, for displacing said output shaft axially with respect to said impeller.