Vacuum pump

Abstract

A vacuum pump may include a regenerative pumping mechanism and a drag pumping mechanism. The regenerative pumping mechanism may include a generally disc-shaped member mounted on an axial shaft for rotation relative to a stator of the regenerative pumping mechanism. The drag pumping mechanism may include a generally cylindrical-shaped member mounted at an outer circumferential portion of the disc-shaped member for rotation about the axial shaft relative to a stator of the drag pumping mechanism.

1 . A vacuum pump comprising:
 a regenerative pumping mechanism comprising a generally disc-shaped member mounted on an axial shaft for rotation relative to a stator of the regenerative pumping mechanism; and   a drag pumping mechanism, the drag pumping mechanism comprising a generally cylindrical-shaped member mounted at an outer circumferential portion of the disc-shaped member for rotation about the axial shaft relative to a stator of the drag pumping mechanism, rotation of the disc-shaped member and the cylindrical-shaped member by the axial shaft causing fluid to flow radially inwardly in series through the drag pumping mechanism and the regenerative pumping mechanism.   
     
     
         2 . The vacuum pump of  claim 1 , wherein the generally disc-shaped member comprises rotor formations on opposing sides of the generally disc-shaped member that are co-operable with complementary portions of the stator of the regenerative pumping mechanism for pumping fluid along parallel fluid flow paths on the opposing sides. 
     
     
         3 . The vacuum pump of  claim 1 , wherein the generally cylindrical-shaped member comprises first and second cylindrical portions extending on opposing axial sides of the generally disc-shaped member co-operable with complementary portions of the stator of the drag pumping mechanism for pumping fluid along parallel fluid flow paths on the first and second cylindrical portions. 
     
     
         4 . The vacuum pump of  claim 2 , wherein the parallel flow paths of the regenerative pumping mechanism are symmetrical about a central plane of the generally disc-shaped member, the parallel flow paths of the drag pumping mechanism are symmetrical about the central plane, or both, such that forces generated during pumping fluid along said parallel flow paths are balanced in the regenerative pumping mechanism, the drag pumping mechanism, or both. 
     
     
         5 . The vacuum pump of  claim 4 , further comprising an axial gas bearing arrangement located at an inner circumference of the generally disc-shaped member for maintaining an axial clearance between the generally disc-shaped member and the stator of the regenerative pumping mechanism. 
     
     
         6 . The vacuum pump of  claim 4 , wherein the axial gas bearing arrangement comprises a first axial gas bearing and a second axial gas bearing on opposite sides of the generally disc-shaped member. 
     
     
         7 . The vacuum pump of  claim 6 , wherein fluid passing along the parallel fluid flow paths is conveyed through at least one of the first or second axial gas bearings towards the outlet of the vacuum pump. 
     
     
         8 . The vacuum pump as claimed in of  claim 6 , wherein fluid passing along the parallel flows paths is diverted along one or more diversions paths in at least one of the generally disc-shaped member or the stator of the regenerative pumping mechanism for by-passing the axial gas bearings. 
     
     
         9 . A The vacuum pump of  claim 1 , wherein the regenerative pumping mechanism comprises a plurality of pumping stages arranged at respective circumferences of the generally disc-shaped member and the rotor formations of the pumping stages decrease in size from an outer circumference towards an inner circumference. 
     
     
         10 . The vacuum pump of  claim 9 , further comprising a blow-off valve for selectively opening a fluid path between a stage of the regenerative pumping mechanism inward from the outer circumference of the generally disc-shaped member and atmosphere for bypassing at least one inner pumping stage from the fluid flow path. 
     
     
         11 . The vacuum pump of  claim 1 , wherein the generally cylindrical member comprises carbon fiber for reducing inertia about the axial shaft. 
     
     
         12 . The vacuum pump of  claim 2 , wherein the generally cylindrical-shaped member comprises first and second cylindrical portions extending on opposing axial sides of the generally disc-shaped member co-operable with complementary portions of the stator of the drag pumping mechanism for pumping fluid along parallel fluid flow paths on the first and second cylindrical portions. 
     
     
         13 . The vacuum pump of  claim 3 , wherein the parallel flow paths of the regenerative pumping mechanism are symmetrical about a central plane of the generally disc-shaped member, the parallel flow paths of the drag pumping mechanism are symmetrical about the central plane, or both, such that forces generated during pumping fluid along said parallel flow paths are balanced in the regenerative pumping mechanism, the drag pumping mechanism, or both. 
     
     
         14 . The vacuum pump of  claim 13 , further comprising an axial gas bearing arrangement located at an inner circumference of the generally disc-shaped member for maintaining an axial clearance between the generally disc-shaped member and the stator of the regenerative pumping mechanism. 
     
     
         15 . The vacuum pump of  claim 13 , wherein the axial gas bearing arrangement comprises a first axial gas bearing and a second axial gas bearing on opposite sides of the generally disc-shaped member. 
     
     
         16 . The vacuum pump of  claim 15 , wherein fluid passing along the parallel fluid flow paths is conveyed through at least one of the first or second axial gas bearings towards the outlet of the vacuum pump. 
     
     
         17 . The vacuum pump of  claim 15 , wherein fluid passing along the parallel flows paths is diverted along one or more diversions paths in at least one of the generally disc-shaped member or the stator of the regenerative pumping mechanism for by-passing the axial gas bearings. 
     
     
         18 . The vacuum pump of  claim 2 , wherein the regenerative pumping mechanism comprises a plurality of pumping stages arranged at respective circumferences of the generally disc-shaped member and rotor formations of the pumping stages decrease in size from an outer circumference towards an inner circumference, further comprising a blow-off valve for selectively opening a fluid path between a stage of the regenerative pumping mechanism inward from the outer circumference of the generally disc-shaped member and atmosphere for bypassing at least one inner pumping stage from the fluid flow path. 
     
     
         19 . The vacuum pump of  claim 3 , wherein the regenerative pumping mechanism comprises a plurality of pumping stages arranged at respective circumferences of the generally disc-shaped member and rotor formations of the pumping stages decrease in size from an outer circumference towards an inner circumference, further comprising a blow-off valve for selectively opening a fluid path between a stage of the regenerative pumping mechanism inward from the outer circumference of the generally disc-shaped member and atmosphere for bypassing at least one inner pumping stage from the fluid flow path. 
     
     
         20 . The vacuum pump of  claim 4 , wherein the regenerative pumping mechanism comprises a plurality of pumping stages arranged at respective circumferences of the generally disc-shaped member and rotor formations of the pumping stages decrease in size from an outer circumference towards an inner circumference, further comprising a blow-off valve for selectively opening a fluid path between a stage of the regenerative pumping mechanism inward from the outer circumference of the generally disc-shaped member and atmosphere for bypassing at least one inner pumping stage from the fluid flow path.