Vacuum Pump Impeller

Abstract

The invention relates to a vacuum pump impeller ( 10 ) which comprises a shaft ( 14 ) made of steel, and a one-piece rotor ( 12 ) supported by the shaft ( 14 ) and made of a material different from the steel of the shaft. The shaft ( 14 ) comprises an axial cavity ( 22 ), and the rotor ( 12 ) comprises an axial projection ( 16 ) seated in the cavity ( 22 ) in positive and/or non-positive engagement therewith.

1 . A vacuum pump impeller comprising: 
 a shaft made of steel, and a one-piece rotor supported by the shaft and made of a material different from the steel of the shaft, shaft defining an axial cavity and the rotor including an axial projection seated in the cavity in positive and/or non-positive engagement therewith.    
     
     
         2 . The vacuum pump impeller according to  claim 1 , wherein the rotor projection and the shaft comprise, within the cavity respectively shaped portions, the shaped portions effecting a positive engagement with each other in the axial direction and the circumferential direction.  
     
     
         3 . The vacuum pump impeller according to claim, wherein the rotor is a cast part having its projection cast into the shaft cavity.  
     
     
         4 . The vacuum pump impeller according to  claim 2 , wherein said shaped portions are formed as grooves and bars.  
     
     
         5 . The vacuum pump impeller according to  claim 1 , wherein on a rotor-side end, the wall thickness of the shaft continuously decreases towards an opening of the cavity.  
     
     
         6 . The vacuum pump impeller according to  claim 1 , wherein the rotor is supported by a single shaft.  
     
     
         7 . The vacuum pump impeller according to  claim 1 , wherein the rotor is formed of a light metal or a plastic material.  
     
     
         8 . The vacuum pump impeller according to  claim 7 , wherein the rotor material is aluminum.  
     
     
         9 . A method for producing a vacuum pump impeller according to  claim 1  by casting, comprising the method steps of: 
 inserting a shaft having an axial shaft cavity into a rotor mold,    filling in the liquid rotor molding material into the rotor mold and into the shaft cavity, and    removing the vacuum pump impeller from the mold after the rotor has set.    
     
     
         10 . A method for producing a vacuum pump impeller according to  claim 1  by forging, comprising the method steps of: 
 inserting a shaft having an axial shaft cavity into a drop-forge die for the rotor,    forging red-hot rotor forging material into the rotor drop-forge die and into the shaft cavity, and    removing the vacuum pump impeller from the drop-forge die.    
     
     
         11 . A vacuum pump impeller comprising: 
 a shaft defining an axial cavity in at least one end thereof;    a rotor constructed of a material which expands radially outward relative to the steel shaft when drawing a vacuum, the rotor including an axial projection which extends into the shaft axial cavity such that when drawing the vacuum, the rotor axial projection expands into a tighter relationship with shift to avoid slippage.    
     
     
         12 . The vacuum pump impeller according to  claim 11 , wherein a thickness of a shaft wall surrounding the axial cavity thins toward the one end that receives the rotor axial projection such that a stiffness of the shaft decreases toward the rotor to reduce fatigue and a risk of the rotor breaking from the shaft.  
     
     
         13 . The vacuum pump impeller according to  claim 11 , further including: 
 mating ridges and grooves defined in an interior of a peripheral wall of the shaft surrounding the axial shaft cavity and the rotor axial projection.    
     
     
         14 . The vacuum pump impeller according to  claim 11 , wherein the rotor axial projection is one of cast or forged into the shaft axial cavity.  
     
     
         15 . The vacuum pump impeller according to  claim 11 , wherein the shaft is constructed of steel and the rotor is constructed of aluminum.