Vacuum exhaust apparatus and drive method of vacuum apparatus

Abstract

Pairs of rotors (R 1 , R 2 , R 3 , R 4 , R 5 and R 6 ) driven rotationally by a motor ( 22 ) are disposed in the body ( 21 ) of a main pump ( 20 ) comprising a multistage Roots dry vacuum pump. A suction opening ( 23 ) communicating with the rotor chamber of the rotor R 1 is provided in the upper wall portion at the left end of the body ( 21 ). A delivery section ( 24 ) communicating with the delivery side of the rotor chamber of rotor R 6 on the final stage is coupled to an exhaust pipe ( 25 ) and is provided with a silencer ( 26 ) and further coupled to a check valve ( 28 ) through a pipe ( 27 ). The check valve ( 28 ) has its forward direction toward the atmospheric side. The delivery section ( 24 ), or a delivery section ( 24 ′) at the side intermediate stage, is coupled to an auxiliary pump ( 30 ) having an exhaust capacity smaller than that of the main pump ( 20 ). When the motor ( 22 ) is driven, gas exhausted through rotation of the rotors (R 1 -R 6 ) is carried sequentially to the downstream side from the rotor chambers and a vacuum processing chamber coupled to the suction opening ( 23 ) is exhausted. The delivery section ( 24 ) on the final stage is exhausted by driving the auxiliary pump ( 30 ), and the pressure is reduced. Consequently, the burden of the exhaust action on the rotor (R 6 ) on the final stage or the rotor (R 5 ) on the intermediate stage is lessened, and the power consumption of the motor ( 22 ) can be reduced significantly as compared with the prior art.

1 . A vacuum exhaust apparatus characterized in that an inlet side of an auxiliary pump is connected to an outlet side of a pump chamber of a middle stage or last stage, of a main pump.  
     
     
         2 . A vacuum exhaust apparatus according to  claim 1  in which the throughput of said auxiliary pump is smaller than that of main pump.  
     
     
         3 . A vacuum exhaust apparatus according to  claim 1  or  2  in which at least one of pump chambers at the latter stage of said main pump is smaller than the pump chambers of the former stage of said main pump so that the throughput of the latter stage is smaller than that of the former stage.  
     
     
         4 . A vacuum exhaust apparatus according to any one of  claims 1  to  3  in which an exhaust pipe is connected to an outlet side of the pump chamber of the last stage of said main pump and a check valve permitting gas to flow only in the direction towards the atmosphere is connected to said exhaust pipe.  
     
     
         5 . A vacuum exhaust apparatus according to  claim 4  in which said check valve consists of plural members serially connected to each other.  
     
     
         6 . A vacuum exhaust apparatus according to  claim 5  in which said check valve includes a first check valve member which includes a ball valve body floatable in a valve chamber, said valve body floats up by an exhaust gas pressure of said main pump to open the valve and it seats on a valve seat by self-weight under said exhaust gas pressure, to close the valve, and a second check valve member similar to said first check valve, said first and second check valve members being serially connected with each other.  
     
     
         7 . A vacuum exhaust apparatus according to any one of  claims 4  to  6  in which said auxiliary pump is connected in parallel with said check valve.  
     
     
         8 . A vacuum exhaust apparatus according to  claim 6  in which a space between said first and second check valve members is connected to the suction side of said auxiliary pump.  
     
     
         9 . A vacuum exhaust apparatus according to  claim 6  in which said ball valve body consists of a hollow metal ball and is coated with rubber.  
     
     
         10 . A vacuum exhaust apparatus characterized in that said apparatus includes a main pump, a check valve permitting gas to flow only in the direction towards the atmosphere, connected to the outlet side of said main pump and an auxiliary pump of smaller throughput than that of said main pump connected in parallel with said check valve at the outlet side of said main pump and said auxiliary pump is driven at the pumping speed lower than 3% of that of said main pump at the inlet pressure 400 Pa of said main pump.  
     
     
         11 . A vacuum exhaust apparatus according to  claim 10  in which said main pump is a dry vacuum pump of the positive displacement type or composite type pump consisting of plural dry vacuum pumps connected serially to each other.  
     
     
         12 . A vacuum exhaust apparatus according to  claim 10  in which a plurality of said main pumps are connected in parallel with each other and the inlet side of said auxiliary pump is connected to the respective outlets of said main pump.  
     
     
         13 . A vacuum exhaust apparatus according to  claim 10  in which the ultimate pressure of said auxiliary pump is under 20 kPa.  
     
     
         14 . A vacuum exhaust apparatus according to  claim 13  in which said auxiliary pump is a sliding-vane type (Gede type), a piston type, a diaphragm type (membrane type) or scroll type.  
     
     
         15 . A vacuum exhaust apparatus characterized in that said apparatus includes a main pump connected to a vacuum processing chamber, a check valve permitting gas to flow only in the direction towards the atmosphere, connected to the outlet side of said main pump and an auxiliary pump of smaller throughout than that of said main pump connected in parallel with said check valve at the outlet side of said main pump, whereby, when said vacuum processing chamber is exhausted form the atmosphere or from near the atmosphere, first said auxiliary pump is driven and after said vacuum processing chamber has reached a predetermined pressure, said main pump is driven.  
     
     
         16 . A vacuum exhaust apparatus characterized in that said apparatus includes a main pump connected to a vacuum processing chamber, a check valve permitting gas to flow only in the direction towards the atmosphere, connected to the outlet side of said main pump and an auxiliary pump of smaller throughput than that of said main pump connected in parallel with said check valve at the outlet side of said main pump, whereby, when said vacuum processing chamber is exhausted from the atmosphere or from near atmosphere, first said auxiliary pump is driven and before said vacuum processing chamber reaches a predetermined pressure, said main pump is started to be driven at the lower speed or the lower pumping speed and the rotational speed is raised in accordance with the pressure of the vacuum processing chamber.