Vacuum pump

Abstract

A vacuum pump includes at least two stages ( 2, 3 ), a motor ( 8 ) for driving pump-active elements of the two stages ( 2, 3 ), a transmission unit ( 7 ) for transmitting driving power from the motor ( 8 ) to the pump-active elements, a motor control ( 9 ) for controlling a rotational speed of the motor ( 8 ), and an evaluation unit ( 12 ) electrically connectable with pressure-sensitive signal sensor ( 10 ) located between the two stages for receiving a signal generated by the signal sensor and connected with the motor control ( 9 ) for transmitting an evaluated signal thereto, so that the motor control ( 9 ) can change a rotational speed of the motor ( 8 ) in accordance with the received evaluated signal.

1 . A vacuum pump, comprising at least two stages ( 2 ,  3 ); a motor ( 8 ) for driving pump-active elements of the two stages ( 2 ,  3 ); a transmission unit ( 7 ) for transmitting driving power from the motor ( 8 ) to the pump-active elements; a motor control ( 9 ) for controlling a rotational speed of the motor ( 8 ); a gas-sensitive signal sensor ( 10 ) located between the two stages ( 2 ,  3 ) for sensing pressure of gas transmittable from one stage ( 2 ) to another stage ( 3 ) and for generating a corresponding signal; and an evaluation unit ( 12 ) electrically connectable with the signal sensor ( 10 ) for receiving the generated signal and evaluating same and connected with the motor control ( 9 ) for transmitting an evaluated signal thereto, the motor control ( 9 ) changing a rotational speed of the motor ( 8 ) in accordance with the received evaluated signal. 
   
   
       2 . A vacuum pump according to  claim 1 , wherein the evaluation unit ( 12 ) is contained in the motor control ( 9 ). 
   
   
       3 . A vacuum pump according to  claim 1 , wherein the signal sensor ( 10 ) is arranged at a gas inlet of pump stage ( 3 ) of the two pump stages ( 2 ,  3 ) that communicates with atmosphere. 
   
   
       4 . A vacuum pump according to  claim 1 , wherein at least one of the at least two pump stages ( 2 ,  3 ) includes a movable seal ( 23 ). 
   
   
       5 . A vacuum pump according to  claim 1 , wherein the vacuum pump ( 1 ) is formed as dry piston vacuum pump. 
   
   
       6 . A vacuum pump according to  claim 5 , wherein the signal sensor ( 10 ) is located in one of annular space ( 28 ) that serves as a gas inlet and at least partially surrounds a cylinder ( 21 ) at least partially at a height of a gas inlet opening ( 27 ) that communicates the annular space ( 28 ) with a compression chamber defined by the cylinder ( 21 ), and in conduit means through which gas flows to the annular space ( 28 ). 
   
   
       7 . A method of operating a vacuum pump ( 1 ) having at least two stages ( 2 ,  3 ), a motor ( 8 ) for driving pump-active elements of the two stages ( 2 ,  3 ), and a motor control ( 9 ) that operates the motor ( 8 ) with at least two different rotational speeds, the method comprising the steps of generating, with a gas-sensitive signal sensor, a signal dependent on gas pressure of gas flow between the two stages ( 2 ,  3 ); evaluating the generated signal; and setting a rotational speed of the motor ( 8 ) by the motor control ( 9 ) dependent on result of evaluation of the generated signal. 
   
   
       8 . A method according to  claim 7 , wherein the rotational speed setting step includes selecting a speed between two predetermined rotational speeds. 
   
   
       9 . A method according to  claim 7 , wherein a rotational speed is reduced in response to a signal corresponding to pressure below atmospheric pressure.