Casing assembly for a gas turbine engine

Abstract

There is described a casing assembly for a gas turbine engine, the casing assembly comprising: an annular casing having a longitudinal axis; a unison ring assembly configured for rotation about the longitudinal axis; a plurality of vanes rotatably coupled to the annular casing; and a plurality of linkages, wherein each of the plurality of vanes is coupled to the unison ring assembly by a respective one of the plurality of linkages. Each linkage comprises: a first link coupled to the respective vane; and a second link rotatably coupled to the first link and rotatably coupled to the unison ring assembly, such that rotation of the unison ring assembly about the longitudinal axis effects rotation of the respective vane.

What is claimed is: 
     
         1 . A casing assembly for a gas turbine engine, the casing assembly comprising:
 an annular casing having a longitudinal axis;   a unison ring assembly configured for rotation about the longitudinal axis;   a plurality of vanes rotatably coupled to the annular casing; and   a plurality of linkages, wherein each of the plurality of vanes is coupled to the unison ring assembly by a respective one of the plurality of linkages, wherein each linkage comprises:
 a first link coupled to the respective vane; and 
 a second link rotatably coupled to the first link and rotatably coupled to the unison ring assembly, such that rotation of the unison ring assembly about the longitudinal axis effects rotation of the respective vane. 
   
     
     
         2 . The casing assembly as claimed in  claim 1 , wherein the unison ring assembly is configured for movement on a single plane. 
     
     
         3 . The casing assembly as claimed in  claim 1 , wherein the second link of each of the linkages is rotatably coupled to its respective first link about a first axis of rotation that is substantially perpendicular to the longitudinal axis. 
     
     
         4 . The casing assembly as claimed in  claim 1 , wherein the second link of each of the linkages is rotatably coupled to the unison ring assembly about a second axis of rotation that is substantially perpendicular to the longitudinal axis. 
     
     
         5 . The casing assembly as claimed in  claim 1 , wherein the first link of each of the linkages is fixedly coupled to its respective vane. 
     
     
         6 . The casing assembly as claimed in  claim 1 , wherein the second link of each of the linkages is rotatably coupled to its respective first link and/or the unison ring assembly by a hinge joint. 
     
     
         7 . The casing assembly as claimed in  claim 1 , wherein the second link of each of the linkages is rotatably coupled to its respective first link and/or the unison ring assembly by a universal joint. 
     
     
         8 . The casing assembly as claimed in  claim 1 , wherein the second link of each of the linkages is rotatably coupled to its respective first link and/or the unison ring assembly by a spherical joint. 
     
     
         9 . The casing assembly as claimed in  claim 1 , wherein two or more of the first links or two or more of the second links have two or more different lengths. 
     
     
         10 . The casing assembly as claimed in  claim 1 , wherein the unison ring assembly comprises two or more unison rings spaced from each other, wherein the second links of each of the linkages are rotatably coupled to the two or more unison rings. 
     
     
         11 . The casing assembly as claimed in  claim 10 , wherein the two or more unison rings are connected by one or more connecting rods. 
     
     
         12 . The casing assembly as claimed in  claim 10 , wherein each of the two or more unison rings comprise a plurality of clevises, wherein the second links of each of the linkages are rotatably coupled to the unison ring assembly via a respective one of the plurality of clevises. 
     
     
         13 . The casing assembly as claimed in  claim 10 , wherein each of the two or more unison rings comprise a plurality of projections extending towards the longitudinal axis, wherein the annular casing comprises a plurality of grooves or slots for receiving the plurality of projections and locating the two or more unison rings relative to the annular casing. 
     
     
         14 . The casing assembly as claimed in  claim 10 , wherein the two or more unison rings are substantially planar. 
     
     
         15 . The casing assembly as claimed in  claim 1 , wherein the plurality of vanes are a plurality of stator vanes and/or a plurality of inlet guide vanes. 
     
     
         16 . A gas turbine engine comprising a casing assembly as claimed in  claim 1 .