by a sleeve like carrier 39 for the purpose of supplying the bearings 35 and 36 with a lubricant a vessel 41 filled with oil 40 is affixed underneath the turbomolecular pump 25 the drive shaft 34 the lower end of which is immersed in the oil exhibits an inner coaxial bore 42 which owing to the conically expanding bottom section 43 effects pumping of the lubricating oil towards the top through cross bores 44 the oil first arrives at the upper bearing 35 and there flows due to the effect of gravity through the bottom bearing 36 back into the oil vessel through the forevacuum port 45 and the line 46 the turbomolecular pump 25 is connected to the forevacuum pumping facility 47 since there exists between the motor bearing chamber 31 and the forevacuum port 45 a connection there also prevails in space 31 the necessary forevacuum pressure needed to operate the turbomolecular pump in order to prevent corrosive gases being pumped by the turbomolecular pump from entering into the bearing chamber 31 a purge gas facility is provided which initially comprises the gas admission pipe 48 opening out into the bearing chamber for the purpose of admitting the purge gas in a controlled manner said gas inlet pipe 48 exhibits a.