Multistage dry vacuum pump

Abstract

A multistage dry vacuum pump includes a housing, pump chambers formed in the housing, each having an inlet and an outlet, a rotor provided in each pump chamber, a shaft connected to each rotor, a rotation driving device connected to the shaft, an intermediate exhaust conduit, one end thereof connected to the outlet of the pump chamber other than the most downstream and the other end thereof opened to outside, and a first fluid flow control device provided in the intermediate exhaust conduit for closing the same when fluid pressure in the outlet side of the pump chamber connected to the intermediate exhaust conduit is lower than that outside the other end of the intermediate exhaust conduit, and for opening the same when fluid pressure is equal to or higher than that outside the same.

1 . A multistage dry vacuum pump, comprising: 
 a housing having a main inlet and a main outlet;    a plurality of pump chambers formed in the housing in series and spatially connecting the main inlet with the main outlet; each pump chamber having an inlet connected to upstream and an outlet connected to downstream;    a plurality of rotors each rotatably provided in the each pump chamber for transporting fluid in a scavenging space defined in the pump chamber through the outlet of the pump chamber to the downstream by rotating;    a shaft connected to each rotor provided in the each pump chamber for rotating the each rotor synchronously;    a rotation driving means connected to the shaft;    an intermediate exhaust conduit, one end thereof being connected to the outlet of the pump chamber located at other than the most downstream side and the other end thereof being opened to outside; and    a first fluid flow control means provided in the intermediate exhaust conduit for closing the intermediate exhaust conduit when the fluid pressure in the one end of the intermediate exhaust conduit is lower than that in the other end of the intermediate exhaust conduit and for opening the intermediate exhaust conduit when the fluid pressure in the one end of the intermediate exhaust conduit is equal to or higher than that in the other end of the intermediate exhaust conduit.    
   
   
       2 . The multistage dry vacuum pump according to  claim 1 , wherein 
 a volume of the scavenging space defined in the each pump chamber becomes smaller sequentially from the pump chamber provided at the upstream side to the pump chamber provided at the downstream side.    
   
   
       3 . The multistage dry vacuum pump according to  claim 1 , further comprising: 
 a main exhaust conduit, one end thereof connected to the outlet of the pump chamber provided at the most downstream side, the other end thereof connected to the main outlet; and    a second fluid flow control means provided in the main exhaust conduit for closing the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is lower than that in the other end of the main exhaust conduit and for opening the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is equal to or higher than that in the other end of the main exhaust conduit.    
   
   
       4 . The multistage dry vacuum pump according to  claim 2 , further comprising: 
 a main exhaust conduit, one end thereof connected to the outlet of the pump chamber provided at the most downstream side, the other end thereof connected to the main outlet; and    a second fluid flow control means provided in the main exhaust conduit for closing the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is lower than that in the other end of the main exhaust conduit and for opening the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is equal to or higher than that in the other end of the main exhaust conduit.    
   
   
       5 . The multistage dry vacuum pump according to  claim 3 , wherein 
 the other end of the intermediate exhaust conduit is connected to the other end of the main exhaust conduit.    
   
   
       6 . The multistage dry vacuum pump according to  claim 4 , wherein 
 the other end of the intermediate exhaust conduit is connected to the other end of the main exhaust conduit.    
   
   
       7 . A multistage dry vacuum pump comprising: 
 a housing having a main inlet and a main outlet;    a plurality of pump chambers formed in the housing in series and spatially connecting the main inlet with the main outlet, each pump chamber having an inlet connected to upstream side and an outlet connected to downstream side;    drive and driven rotors provided rotatably in the each pump chamber, the drive rotor and the driven rotor transporting fluid in a scavenging space defined in the pump chamber through the outlet of the pump chamber to the downstream by synchronously rotating;    a drive shaft connected to each drive rotor provided in the each pump chamber for synchronously rotating the each drive rotor;    a driven shaft connected to each dependent rotor provided in the each pump chamber for synchronously rotating the each dependent rotor;    a rotation driving means connected to the drive shaft;    a transmitting means for transmitting rotation of the drive shaft to the driven shaft;    an intermediate exhaust conduit, one end thereof being connected to the outlet of the pump chamber located at other than the most downstream side and the other end thereof being opened to outside; and    a first fluid flow control means provided in the intermediate exhaust conduit for closing the intermediate exhaust conduit when the fluid pressure in the one end of the intermediate exhaust conduit is lower than that in the other end of the intermediate exhaust conduit and for opening the intermediate exhaust conduit when the fluid pressure in the one end of the intermediate exhaust conduit is equal to or higher than that in the other end of the intermediate exhaust conduit.    
   
   
       8 . The multistage dry vacuum pump according to  claim 7 , wherein 
 a volume of the scavenging space defined in the each pump chamber becomes smaller sequentially from the pump chamber provided at the upstream side to the pump chamber provided at the downstream side.    
   
   
       9 . The multistage dry vacuum pump according to  claim 7 , further comprising: 
 a main exhaust conduit, one end thereof connected to the outlet of the pump chamber provided at the most downstream side, the other end thereof connected to the main outlet; and    a second fluid flow control means provided in the main exhaust conduit for closing the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is lower than that in the other end of the main exhaust conduit and for opening the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is equal to or higher than that in the other end of the main exhaust conduit.    
   
   
       10 . The multistage dry vacuum pump according to  claim 8 , further comprising: 
 a main exhaust conduit, one end thereof connected to the outlet of the pump chamber provided at the most downstream side, the other end thereof connected to the main outlet; and    a second fluid flow control means provided in the main exhaust conduit for closing the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is lower than that in the other end of the main exhaust conduit and for opening the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is equal to or higher than that in the other end of the main exhaust conduit.    
   
   
       11 . The multistage dry vacuum pump according to  claim 9 , wherein 
 the other end of the intermediate exhaust conduit is connected to the other end of the main exhaust conduit.    
   
   
       12 . The multistage dry vacuum pump according to  claim 10 , wherein 
 the other end of the intermediate exhaust conduit is connected to the other end of the main exhaust conduit.    
   
   
       13 . A multistage dry vacuum pump comprising: 
 a housing having a main inlet and a main outlet;    a plurality of pump chambers formed in the housing in series and spatially connecting the main inlet with the main outlet, each pump chamber having an inlet connected to upstream side and an outlet connected to downstream side;    a plurality of rotors each rotatably provided in the each pump chamber for transporting fluid in a scavenging space defined in the pump chamber from the outlet of the pump chamber to the downstream by rotating;    a shaft connected to each rotor provided in the each pump chamber for rotating the each rotor synchronously;    a rotation driving means connected to the shaft; and    a pressure adjusting means for adjusting the fluid pressure in the outlet side of the pump chamber to be equal to or lower than atmospheric pressure.    
   
   
       14 . The multistage dry vacuum pump according to  claim 13 , wherein 
 the pressure adjusting means adjusts the fluid pressure in the outlet side of the pump chamber equal to or lower than the atmospheric pressure by opening the outlet side of the pump chamber when the fluid pressure in the outlet side of the pump chamber is higher than the atmospheric pressure.    
   
   
       15 . The multistage dry vacuum pump according to  claim 14 , wherein 
 the pressure adjusting means includes an intermediate exhaust conduit, one end thereof being connected to the outlet of the pump chamber located at other than the most downstream side and the other end thereof being opened to outside; and    a first fluid flow control means provided in the intermediate exhaust conduit for closing the intermediate exhaust conduit when the fluid pressure in the one end of the intermediate exhaust conduit is lower than that in the other end of the intermediate exhaust conduit and for opening the intermediate exhaust conduit when the fluid pressure in the one end of the intermediate exhaust conduit is equal to or higher than that in the other end of the intermediate exhaust conduit.    
   
   
       16 . The multistage dry vacuum pump according to  claim 13 , wherein 
 a volume of the scavenging space defined in the each pump chamber becomes smaller sequentially from the pump chamber provided at the upstream side to the pump chamber provided at the downstream side.    
   
   
       17 . The multistage dry vacuum pump according to  claim 15 , further comprising: 
 a main exhaust conduit, one end thereof connected to the outlet of the pump chamber provided at the most downstream side, the other end thereof connected to the main outlet; and    a second fluid flow control means provided in the main exhaust conduit for closing the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is lower than that in the other end of the main exhaust conduit and for opening the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is equal to or higher than that in the other end of the main exhaust conduit.    
   
   
       18 . The multistage dry vacuum pump according to  claim 16 , further comprising: 
 a main exhaust conduit, one end thereof connected to the outlet of the pump chamber provided at the most downstream side, the other end thereof connected to the main outlet; and    a second fluid flow control means provided in the main exhaust conduit for closing the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is lower than that in the other end of the main exhaust conduit and for opening the main exhaust conduit when the fluid pressure in the one end of the main exhaust conduit is equal to or higher than that in the other end of the main exhaust conduit.    
   
   
       19 . The multistage dry vacuum pump according to  claim 15 , wherein 
 the other end of the intermediate exhaust conduit is connected to the other end of the main exhaust conduit.    
   
   
       20 . The multistage dry vacuum pump according to  claim 16 , wherein 
 the other end of the intermediate exhaust conduit is connected to the other end of the main exhaust conduit.