Vacuum pumping arrangement

Abstract

A vacuum pumping arrangement comprises a drive shaft, a motor for driving said drive shaft, a molecular pumping mechanism and a regenerative pumping mechanism. The drive shaft is arranged for simultaneously driving the molecular pumping mechanism and the regenerative pumping mechanism. The drive shaft is supported by a lubricant free bearing associated with the molecular pumping mechanism.

1 . A vacuum pumping arrangement comprising a drive shaft, a motor for driving the drive shaft, a molecular pumping mechanism and a regenerative pumping mechanism, wherein the drive shaft is arranged for simultaneously driving the molecular pumping mechanism and the regenerative pumping mechanism and the drive shaft is supported by a lubricant free bearing associated with the molecular pumping mechanism.  
     
     
         2 . The arrangement as claimed in  claim 1 , wherein the lubricant free bearing is a magnetic bearing.  
     
     
         3 . The arrangement as claimed in  claim 1 , wherein the lubricant free bearing and the molecular pumping mechanism are substantially axially aligned.  
     
     
         4 . The arrangement as claimed in  claim 1 , wherein the drive shaft is additionally supported by a lubricated bearing associated with the regenerative pumping mechanism.  
     
     
         5 . The arrangement as claimed in  claim 4 , wherein the lubricated bearing is a rolling bearing.  
     
     
         6 . The arrangement as claimed in  claim 4 , wherein the lubricated bearing and the regenerative pumping mechanism are substantially axially aligned.  
     
     
         7 . The arrangement as claimed in  claim 4 , wherein the regenerative pumping mechanism comprises a stator comprising a plurality of circumferential pumping channels disposed about a longitudinal axis of the drive shaft and a rotor comprising a plurality of arrays of rotor blades extending axially into the respective circumferential pumping channels.  
     
     
         8 . The arrangement as claimed in  claim 7 , wherein the rotor of the regenerative pumping mechanism is connected to the drive shaft so as to be sufficiently close to the lubricated bearing so that radial movement of the drive shaft at the lubricant free bearing translates substantially to axial movement of the rotor blades relative to the respective circumferential pumping channels.  
     
     
         9 . The arrangement as claimed in  claim 7 , wherein the lubricated bearing and the circumferential pumping channels are substantially axially aligned.  
     
     
         10 . The arrangement as claimed in  claim 7 , wherein the lubricated bearing is housed in the stator of the regenerative pumping mechanism.  
     
     
         11 . The arrangement as claimed in  claim 1 , wherein the molecular pumping mechanism comprises a molecular drag pumping mechanism.  
     
     
         12 . The arrangement as claimed in  claim 1 , wherein the molecular pumping mechanism comprises turbomolecular pumping means.  
     
     
         13 . The arrangement as claimed in  claim 1 , comprising a housing which houses the molecular pumping mechanism, the regenerative pumping mechanism, the drive shaft and the motor.  
     
     
         14 . A vacuum pumping arrangement comprising a drive shaft, a motor for driving the drive shaft, and a regenerative pumping mechanism, the drive shaft being supported towards one end thereof by a lubricant free bearing and towards the other end thereof by a lubricated bearing, the regenerative pumping mechanism comprising a stator comprising a plurality of circumferential pumping channels disposed about a longitudinal axis of the drive shaft and a rotor comprising a plurality of arrays of rotor blades extending axially into the respective circumferential pumping channels, the rotor being connected to the drive shaft so as to be sufficiently close to the lubricated bearing so that radial movement of the drive shaft at the lubricant free bearing translates substantially to axial movement of the rotor blades relative to the respective circumferential pumping channels.  
     
     
         15 . The arrangement as claimed in  claim 2 , wherein the molecular pumping mechanism comprises a molecular drag pumping mechanism.  
     
     
         16 . The arrangement as claimed in  claim 15 , wherein the molecular pumping mechanism comprises turbomolecular pumping means.  
     
     
         17 . The arrangement as claimed in  claim 16 , comprising a housing which houses the molecular pumping mechanism, the regenerative pumping mechanism, the drive shaft and the motor.