Combination of two interconnected shafts for high-speed rotors

Abstract

This patent presents the invention of a shaft joint with an Inverse Conical Stopper. The joint is a combination of interconnected shafts. The joint is between two shafts. In the joint, one shaft is inserted into the other. The interface between the two shafts can be of any type: press-fit, thermally shrank, threaded, etc. The Inverse Conical Stopper: Prevents swelling of the joint; Enforces concentric alignment of the two shafts; and Pre-stresses the interface. Besides, the shaft-to-shaft interface can be also either bonded or non-bonded. In the former case, the Inverse Conical Stopper also prevents failure of the bond by: Reducing loads on the bond by using the pre-stress to (partly) compensate for the centrifugal load. The Inverse Conical Stopper makes the joint particularly suitable for high centrifugal loads and high rotation speeds.

1 . A combination comprising:
 two interconnected shafts, of which one shaft has a hollow end part having a butt end with an end surface, and the other shaft has an end part with a reduced cross section that is inserted into the hollow end part and has a step between the end part and the rest of the shaft, which step has a surface that is in contact with the end surface of the butt end, wherein the inner surface of the hollow end part is connected to the outer surface of the end part with a reduced cross section by connection means, wherein the end surface of the butt end and the surface of the step are inclined towards a centerline of the shafts.   
     
     
         2 . The combination  claim 1 , wherein the end surfaces of the butt end and the step are any or a combination of flat and non-flat surfaces, surfaces with and without patterns, smooth and rough surfaces. 
     
     
         3 . The combination of  claim 1 , wherein the connection means comprise a glue between the inner surface of the hollow end part and the outer surface of the end part with a reduced cross section. 
     
     
         4 . The combination of  claim 1 , wherein the connection means comprise at least or a combination of gluing, brazing and a tread-locking substance. 
     
     
         5 . The combination of  claim 1 , wherein the connection means comprises a screw thread on the inner surface of the hollow end part and on the outer surface of the end part with a reduced cross section. 
     
     
         6 . The combination of  claim 1 , wherein connection means comprise at least or a combination of screw thread, press fitting, thermal shrinking or application of a lock. 
     
     
         7 . The combination of  claim 1 , wherein the connection means has a surface that is a cylindrical surface. 
     
     
         8 . The combination of  claim 1 , wherein the connection means has a surface that is a conical surface. 
     
     
         9 . The combination of  claim 1 , wherein at least one shaft is hollow. 
     
     
         10 . The combination of  claim 1 , wherein at least one shaft is solid. 
     
     
         11 . The combination of  claim 1 , wherein at least one shaft has an insert. 
     
     
         12 . The combination of  claim 1 , wherein one shaft is hollow with no insert and the other shaft is solid, wherein the solid shaft has a cavity hollowing out its end part with a reduced cross section. 
     
     
         13 . A composed rotor comprising:
 two solid shafts and at least one hollow shaft, wherein one of the solid shafts and the hollow shaft constitute a combination comprising two interconnected shafts, of which one shaft has a hollow end part having a butt end with an end surface, and the other shaft has an end part with a reduced cross section that is inserted into the hollow end part and has a step between the end part and the rest of the shaft, which step has a surface that is in contact with the end surface of the butt end, wherein the inner surface of the hollow end part is connected to the outer surface of the end part with a reduced cross section by connection means, wherein the end surface of the butt end and the surface of the step are inclined towards a centerline of the shafts, while the other solid shaft is connected to the hollow shaft via a long threaded joint.   
     
     
         14 . A micro-turbine based turbogenerator comprising:
 a generator rotor, a compressor rotor, and a turbine rotor connected into a composed rotor comprising:   two solid shafts and at least one hollow shaft;   wherein one of the solid shafts and the hollow shaft constitute a combination comprising two interconnected shafts, of which one shaft has a hollow end part having a butt end with an end surface, and the other shaft has an end part with a reduced cross section that is inserted into the hollow end part and has a step between the end part and the rest of the shaft;   which step has a surface that is in contact with the end surface of the butt end; and   wherein the inner surface of the hollow end part is connected to the outer surface of the end part with a reduced cross section by connection means, wherein the end surface of the butt end and the surface of the step are inclined towards a centerline of the shafts, while the other solid shaft is connected to the hollow shaft via a long threaded joint.