A multiple stage turbomolecular pump with inter-stage inlet

Abstract

A multiple stage turbomolecular pump is disclosed. The pump comprises: a higher vacuum stage comprising a plurality of rotor blade rows; a lower vacuum stage comprising a plurality of rotor blade rows of a larger diameter than the rotor blade rows of the higher vacuum stage; an inter-stage inlet for inputting gas into the turbomolecular pump between the higher vacuum and lower vacuum stages the inlet extending from an outer circumference of the pump to a radial position inside of the larger diameter and comprising a gas directing formation for directing the gas for entry into the pump in an axial direction.

1 . A multiple stage turbomolecular pump comprising:
 a higher vacuum stage comprising a plurality of rotor blade rows;   a lower vacuum stage comprising a plurality of rotor blade rows of a larger diameter than said rotor blade rows of said higher vacuum stage;   an inter-stage inlet for inputting gas into said turbomolecular pump between said higher vacuum and lower vacuum stages said inlet extending from an outer circumference of said pump to a radial position inside of said larger diameter and comprising a gas directing formation for directing said gas for entry into said pump in an axial direction.   
     
     
         2 . The multiple stage turbomolecular pump according to  claim 1 , wherein said inlet comprises said gas directing formation and at least one aperture, said at least one aperture being located at a radial outer position of said pump between said larger diameter and a diameter of at least one rotor of said higher vacuum stage. 
     
     
         3 . The multiple stage turbomolecular pump according to  claim 2 , wherein said at least one aperture is in a plane substantially perpendicular to an axis of said pump. 
     
     
         4 . The multiple stage turbomolecular pump according to  claim 2 , wherein said pump comprises multiple apertures located at different locations around a circumference of said pump. 
     
     
         5 . The multiple stage turbomolecular pump according to  claim 1 , wherein at least a portion of said gas directing formation comprises a substantially axially oriented surface wherein said gas directing formation comprises a surface that changes from a substantially radially oriented surface at an outer circumference of said pump to a substantially axially oriented surface at a radially innermost point of said gas directing formation. 
     
     
         6 . (canceled) 
     
     
         7 . The multiple stage turbomolecular pump according to  claim 1 , wherein at least a portion of said gas directing formation is adjacent to or formed by an outer circumference of a portion of said higher vacuum stage. 
     
     
         8 . The multiple stage turbomolecular pump according to  claim 1 , said pump comprises a stator bridge component for bridging between a smaller diameter stator in said higher vacuum stage and a larger diameter stator in said lower vacuum stage, said stator bridge component comprising a ring in a plane substantially perpendicular to an axis of said pump, said ring comprising multiple apertures. 
     
     
         9 . The multiple stage turbomolecular pump according to  claim 8 , wherein an inner diameter of said ring comprises a diameter of a stator of said higher vacuum stage and an outer diameter of said ring comprises a larger diameter of said stator in said lower vacuum stage. 
     
     
         10 . The multiple stage turbomolecular pump according to  claim 7 , wherein said stator bridge comprises a height that is equal to or greater than the distance between two adjacent rotor blade rows and equal to or less than the distance between two rotor blade rows that are not adjacent but are separated from each other by a rotor blade row. 
     
     
         11 . The multiple stage turbomolecular pump according to  claim 1 , wherein at least some of said rotor blade rows within said higher vacuum stage have different diameters, a diameter of at least one rotor towards said lower vacuum stage being smaller than a diameter of a rotor that is more remote from said lower vacuum stage, wherein said rotor blade rows within said higher vacuum stage have diameters that taper towards said lower vacuum stage. 
     
     
         12 . (canceled) 
     
     
         13 . The multiple stage turbomolecular pump according to  claim 1 , wherein each of said rotor blade rows have multiple blades, said blades of said inter-stage inlet rotor blade row, said inter-stage inlet rotor blade row being said rotor blade row of said lower vacuum stage adjacent to said inter-stage inlet, having an angle of an outer portion of said blades adapted for pumping said gas received at said inter-stage inlet and an angle of an inner portion adapted for pumping said gas received at an inlet of said higher vacuum stage. 
     
     
         14 . The multiple stage turbomolecular pump according to  claim 13 , wherein said blades of said inter-stage inlet rotor have a localised change in geometry between said portion adapted for pumping said gas received at said inter-stage inlet and said portion adapted for pumping said gas received at said higher vacuum stage inlet, said localised change in geometry occurring over a length of said rotor blade that is less than 10% of a radius of said rotor blade, said length of said rotor being in a region of said rotor blade that extends for 20% of said radius of said rotor blade inwardly from a radial point inside of said inlet aperture by 5% of said aperture length. 
     
     
         15 . (canceled) 
     
     
         16 . The multiple stage turbomolecular pump according to  claim 13 , wherein said angle of said outer portion of said blades are adapted for increased pumping speed of said gas received at said inter-stage inlet and said angle of said inner portion are adapted for increased compression of said gas received at an inlet of said higher vacuum stage, wherein an angle between a radial plane, that is a plane perpendicular to said axis of said pump, and said outer portion of said blade is greater than an angle between said radial plane and said inner portion of said blade. 
     
     
         17 . (canceled) 
     
     
         18 . The multiple stage turbomolecular pump according to  claim 1 ,
 wherein each of said rotor blade rows have multiple blades, said blades of said inter-stage inlet rotor blade row, said inter-stage inlet rotor blade row being said rotor blade row of said lower vacuum stage adjacent to said inter-stage inlet, having at least some of said blades of a smaller diameter than said larger diameter.   
     
     
         19 . The multiple stage turbomolecular pump according to  claim 1 ,
 comprising a plurality of stator blade rows, said blades of said inter-stage inlet stator blade row, said inter-stage inlet stator blade row being said stator blade row of said lower vacuum stage adjacent to said inter-stage inlet, having an angle of an outer portion of said blades adapted for the pumping of gas received at said inter-stage inlet and an angle of an inner portion adapted for the pumping of gas received at an inlet of said higher vacuum stage.   
     
     
         20 . The multiple stage turbomolecular pump according to  claim 19 , wherein said blades of said inter-stage inlet stator have a localised change in geometry between said portion adapted for said gas received at said inter-stage inlet and said portion adapted for said gas received at said higher vacuum stage inlet, said localised change in geometry occurring over a length of said stator blade that is less than 10% of a radius of said stator blade. 
     
     
         21 . The multiple stage turbomolecular pump according to  claim 20 , said length being in a region of said stator blade that extends for 20% of said radius of said stator blade inwardly from a radial point inside of said inlet aperture by 5% of said aperture length. 
     
     
         22 . The multiple stage turbomolecular pump according to  claim 19 , wherein said angle of said outer portion of said blades are adapted for increased pumping speed of said gas received at said inter-stage inlet and an angle of an inner portion are adapted for increased compression of said gas received at an inlet of said higher vacuum stage. 
     
     
         23 . The multiple stage turbomolecular pump according to  claim 1 ,
 wherein each of said stator blade rows have multiple blades, said blades of said inter-stage inlet stator blade row, said inter-stage inlet stator blade row being said stator blade row of said lower vacuum stage adjacent to said inter-stage inlet, having an increased number of blades at an outer diameter compared to a number of blades at an inner diameter of said blade row.   
     
     
         24 . The multiple stage turbomolecular pump according to  claim 1 , wherein said higher vacuum stage is a first stage of said pump and said lower vacuum stage is a second stage of said pump, said first stage comprising an inlet that extends across a diameter of said rotor blade rows of said first stage.