VACUUM PUMP IMPELLER

摘要

An impeller (10) for a turbomolecular vacuum pump comprises a shaft (12) having mounted thereon a plurality of rotor elements (14, 16). Part of the shaft (12) extends around magnetic bearing means (20) located within a bore of the shaft (12). At least this part of the shaft (12) is formed from titanium or an alloy thereof so that the bearing means (20) can remain in compression during use of the impeller (10), thereby inhibiting cracking of the bearing means (20).