Vacuum pumps with auxiliary pumping stages

Abstract

Vacuum pumping apparatus includes a housing, one or more primary pumping stages disposed in the housing, a motor coupled to the primary pumping stages, the motor including at least one stationary surface and at least one moving surface when the motor is energized, the stationary and moving surfaces of the motor defining an auxiliary pumping stage coupled in series with the primary pumping stages to pump gas through a pumping channel between the stationary and moving surfaces of the motor, the housing having a first exhaust port between the primary pumping stages and the auxiliary pumping stage, and a second exhaust port at an outlet of the auxiliary pumping stage, and a valve connected in series with the first exhaust port and configured to close when an inlet pressure of the vacuum pumping apparatus is below a predetermined pressure.

1 . Vacuum pumping apparatus comprising:
 a housing;   one or more primary pumping stages disposed in the housing;   a motor coupled to the primary pumping stages, the motor including at least one stationary surface and at least one moving surface when the motor is energized, the stationary and moving surfaces of the motor defining an auxiliary pumping stage coupled in series with the primary pumping stages to pump gas through a pumping channel between the stationary and moving surfaces of the motor;   the housing having a first exhaust port between the primary pumping stages and the auxiliary pumping stage, and a second exhaust port at an outlet of the auxiliary pumping stage; and   a valve connected in series with the first exhaust port and configured to close when an inlet pressure of the vacuum pumping apparatus is below a predetermined pressure.   
   
   
       2 . Vacuum pumping apparatus as defined in  claim 1 , wherein the motor includes a stator and a rotor and wherein the stationary and moving surfaces comprise stator and rotor surfaces, respectively. 
   
   
       3 . Vacuum pumping apparatus as defined in  claim 1 , wherein the motor includes a bearing preload nut and wherein the stationary and moving surfaces comprise housing and bearing preload nut surfaces, respectively. 
   
   
       4 . Vacuum pumping apparatus as defined in  claim 1 , wherein the motor includes a shaft and wherein the stationary and moving surfaces comprise housing and shaft surfaces, respectively. 
   
   
       5 . Vacuum pumping apparatus as defined in  claim 1 , wherein the auxiliary pumping stage comprises a screw-type pumping stage 
   
   
       6 . Vacuum pumping apparatus as defined in  claim 1 , wherein the auxiliary pumping stage comprises a molecular drag stage. 
   
   
       7 . Vacuum pumping apparatus as defined in  claim 2 , wherein the auxiliary pumping stage includes a helical groove in the rotor. 
   
   
       8 . Vacuum pumping apparatus as defined in  claim 2 , wherein the auxiliary pumping stage includes a helical groove in the stator. 
   
   
       9 . Vacuum pumping apparatus as defined in  claim 1 , wherein the primary pumping stages comprise one or more turbomolecular pumping stages. 
   
   
       10 . Vacuum pumping apparatus as defined in  claim 1 , wherein the primary pumping stages include one or more molecular drag pumping stages. 
   
   
       11 . Vacuum pumping apparatus as defined in  claim 1 , wherein the primary pumping stages include one or more turbomolecular pumping stages and one or more molecular drag pumping stages. 
   
   
       12 . Vacuum pumping apparatus as defined in  claim 1 , wherein the valve is automatically closed when the inlet pressure of the vacuum pumping apparatus is below the predetermined pressure. 
   
   
       13 . Vacuum pumping apparatus as defined in  claim 1 , further comprising a roughing vacuum pump coupled to the first exhaust port. 
   
   
       14 . A method for operating vacuum pumping apparatus of the type including a housing, one or more primary pumping stages disposed in the housing and a motor to operate the primary pumping stages, the motor including at least one stationary surface and at least one moving surface when the motor is energized, the method comprising:
 defining an auxiliary pumping stage, coupled in series with the primary pumping stages, to pump gas through a pumping channel between the stationary and moving surfaces of the motor;   exhausting gas from the vacuum pumping apparatus through a first exhaust port between the primary pumping stages and the auxiliary pumping stage when an inlet pressure of the vacuum pumping apparatus is above a predetermined pressure; and   exhausting gas from the vacuum pumping apparatus through a second exhaust port at an outlet of the auxiliary pumping stage when an inlet pressure of the vacuum pumping apparatus is below the predetermined pressure.   
   
   
       15 . The method as defined in  claim 14 , further comprising automatically closing a valve coupled to the first exhaust when the inlet pressure of the vacuum pumping apparatus is below the predetermined pressure. 
   
   
       16 . The method as defined in  claim 14 , wherein the motor includes a stator and a rotor and wherein the stationary and moving surfaces comprise stator and rotor surfaces, respectively. 
   
   
       17 . The method as defined in  claim 14 , wherein the motor includes a bearing preload nut and wherein the stationary and moving surfaces comprise housing and bearing preload nut surfaces, respectively. 
   
   
       18 . The method as defined in  claim 14 , wherein the motor includes a shaft and wherein the stationary and moving surfaces comprise housing and shaft surfaces, respectively.