Damped intershaft bearing and stabilizer

Abstract

A viscous damper for a bearing mounted between coaxially mounted shafts rotating at relative speeds is stabilized by mounting a spring in parallel with the damper so as to raise the natural frequency of one of the shafts.

We claim: 
     
       1. Damping means for an inner shaft and outer shaft mounted in coaxial relation, bearing means mounted between said inner shaft and said outer shaft, a fluid damper mounted under the bearing and includes an annular groove surrounding at least one of said shafts which is filled with a viscous fluid, radial restraint means mounted on said one of said shafts in parallel with the viscous damper means to impart a load to the other of said shafts to change its critical speed to a value above the maximum rotational speed of said one of said shafts and stabilize the viscous damper. 
     
     
       2. Damping means as claimed in claim 1 wherein said radial restraint means includes ring-like elements spaced on opposite ends of said annular groove and are sandwiched between said bearing means and said one of said shafts. 
     
     
       3. Damping means as claimed in claim 2 wherein said ring-like elements are made from an elastomeric material. 
     
     
       4. Damping means as claimed in claim 2 wherein said ring-like elements are made from a metallic material. 
     
     
       5. Damping means as claimed in claim 1 wherein said radial restraint means includes a cylinder-like element surrounding said one of said shafts having one end attached to said one of said shafts and the other end attached to said bearing means forming a cantilever spring. 
     
     
       6. In combination, inner and outer coaxially mounted shafts for a twin spool gas turbine power plant, a roller bearing between said shafts including an inner race adjacent said inner shaft, a race supporting ring secured to said inner shaft to rotate therewith supporting said inner race, a viscous damper including pressurized viscous fluid in an annular space between said shaft and said race supporting ring, axial extension portions on said race supporting ring radially spaced from said inner shaft, spring means mounted in said space to add stiffness in parallel with said viscous damper through said bearing means to said outer shaft to increase its critical speed relative to said inner shaft maximum speed whereby said viscous damper is rendered stable. 
     
     
       7. In combination as in claim 6 wherein said spring means includes an elastomeric ring-like element flexible radially. 
     
     
       8. In combination as in claim 6 wherein said spring means includes a metallic spring-like element flexible radially. 
     
     
       9. In combination, inner and outer coaxially mounted shafts for a twin spool gas turbine power plant, a roller bearing between said shafts including an inner race adjacent said inner shaft, a race supporting ring secured to said inner shaft to rotate therewith supporting said inner race, a viscous damper including pressurized viscous fluid in an annular space between said shaft and said race supporting ring, a sleeve secured to said inner shaft to rotate therewith between said race supporting ring and inner shaft, spring means interconnecting said sleeve and said race supporting ring to add stiffness in parallel with said viscous damper through said bearing means to said outer shaft to increase its critical speed relative to said inner shaft whereby said viscous bearing is rendered stable. 
     
     
       10. In combination as in claim 9 where said sleeve includes a flange axially spaced from said race supporting ring and one end of said spring means is secured to said flange and its opposing end is secured to said race supporting ring. 
     
     
       11. In combination as in claim 10 wherein said spring means includes a cylindrical member having hub-like opposing ends with one end secured to said flange and the other end secured to said race supporting ring, and rod-like elements extending between said hub-like opposing ends deflectable in a radial direction.