Vacuum pump

Abstract

The present invention provides a vacuum pump having a small possibility of causing a damage of a rotor, excellent in working efficiency of the balancing of the rotor, and capable of keeping the balance during a long period of time. A ring shape groove is formed at a lower portion side internal surface of a rotor along the circumferential direction of the rotor. A weight for catching the balance of the rotor is fitted in and attached to the ring shape groove. Accordingly, there is no change of the section and no notch in the circumferential direction of the outer circumference of the rotor so that the stress concentration or the like is not caused and the maximum stress of the rotor is reduced, whereby the damage of the rotor is not easily caused.

What is claimed is:  
     
         1 . A vacuum pump comprising: 
 a pump case forming an inlet port at an upper surface;    a rotor provided rotatably in the pump case;    rotor blades provided integrally with an outer circumferential surface of the rotor;    stator blades positioned and arranged between the rotor blades or at the outside thereof;    a driving motor for rotating the rotor; and    a ring shape groove formed at an internal surface of a lower portion side of the rotor.    
     
     
         2 . A vacuum pump according to  claim 1 , the vacuum pump further comprising a weight is fit in and attached to the ring shape groove.  
     
     
         3 . A vacuum pump according to  claim 2 , wherein the ring shape groove forms a dovetail groove.  
     
     
         4 . A vacuum pump according to  claim 3 , wherein the weight is press fit to the dovetail groove.  
     
     
         5 . A vacuum pump according to  claim 2 , wherein the internal surface of the rotor, from a lower portion opening end of the rotor to the ring shape groove, is cut to provide a cut out portion formed thereby.  
     
     
         6 . A vacuum pump according to  claim 2 , wherein the plurality of ring shape grooves are provided in a vertical direction of the rotor.  
     
     
         7 . A vacuum pump according to  claim 2 , wherein when the weight is accommodated in a box body provided with leaf spring members on both sides thereof, and the body box including the weight is inserted and set in the ring shape groove, the leaf spring members of the body box cause an elasticity return and are pressed by the inner walls of the ring shape groove to be in contact therewith, whereby the weight together with the box body is fitted in and attached to the ring shape groove.  
     
     
         8 . A vacuum pump according to  claim 2 , wherein the leaf spring member is folded into a U-shape, a holder including pinching pieces is used, which are constituted by further folding back externally the both sides of the folded end, and the weight is fixed integrally to the inner side bottom portion formed in a U-shape of the holder, and 
 that when the holder including the weight is inserted and set in the ring shape groove, the pinching pieces of the holder cause an elasticity return to be pressed by the inner walls of the ring shape groove to be in contact therewith, whereby the weight together with the holder is fitted in and attached to the ring shape groove.