Single-Shaft Vacuum Positive Displacement Pump

Abstract

A single-shaft vacuum positive displacement pump ( 10 ) comprises two pump stages ( 12,14 ) each provided with a pump rotor ( 13,15 ) and a drive motor ( 16 ). The drive motor ( 16 ) is axially arranged between the two pump stages ( 12,14 ), wherein the shaft ( 22 ) supports the pump rotors ( 13,15 ) and the motor rotor ( 17 ).

1 . A single-shaft vacuum positive displacement pump comprising:
 two pump stages, each stare including a pump rotor; and   a drive motor said drive motor being axially arranged between said two pump stages, and a shaft supporting pump rotors of said pump stages and a motor rotor.   
   
   
       2 . The single-shaft positive displacement pump according to  claim 1 , wherein a gas connection between the two pumps stages is defined by a gap between the motor rotor and a motor stator. 
   
   
       3 . The single-shaft positive displacement pump according to  claim 2 , wherein the gap between the motor rotor and the motor stator is cylindrical. 
   
   
       4 . The single-shaft positive displacement pump according to  claim 2 , wherein the motor rotor comprises a helical pump groove. 
   
   
       5 . The single-shaft positive displacement pump according to  claim 1 , wherein a stator housing surrounds the shaft, wherein the stator housing does not comprise any sealings. 
   
   
       6 . The single-shaft positive displacement pump according to  claim 1 , wherein exactly two roller bearings are provided between the motor rotor and the pump rotors. 
   
   
       7 . The single-shaft positive displacement pump according to  claim 1 , wherein a stator housing is surrounded by a lubricant housing. 
   
   
       8 . The single-shaft positive displacement pump according to  claim 1 , wherein the motor rotor acts as a lubricant pump which pumps a lubricant from a high-vacuum one of the pump stages to a downstream pre-vacuum one of the pump stages. 
   
   
       9 . The single-shaft positive displacement pump according to  claim 1 , wherein the two pump stages are configured as rotary piston or rotary vane pump stages. 
   
   
       10 . The single-shaft positive displacement pump according to  claim 1 , wherein a first bearing and a first of the pump stage rotors are supported on the shaft on one side of the motor rotor and a second bearing and a second of the pump stage rotors are supported on the shaft on an opposite side of the motor rotor. 
   
   
       11 . A pump comprising:
 a motor stator;   a motor rotor rotatably mounted in the motor stator on a shaft, the motor rotor and the motor stator defining a fluid passage therebetween;   a first pump stage having a rotor mounted on the shaft on one side of the rotor to pump fluid from a fluid inlet into the fluid passage between the motor rotor and the motor stator; and   a second pump stage having a rotor mounted on the shaft on an opposite side of the rotor from the first pump stage rotor to pump fluid from the fluid passage between the motor rotor and the motor stator to an outlet.   
   
   
       12 . The pump according to  claim 11  further including:
 a first bearing supporting the shaft between the motor rotor and the first pump stage rotor; and   a second bearing supporting the shaft between the motor rotor and the second pump stage rotor.