Pitch control of contra-rotating airfoil blades

Abstract

A pitch control mechanism for an open rotor gas turbine engine is provided, the engine having a first rotor assembly and a second rotor assembly, with a plurality of airfoil blades circumferentially mounted on each rotor assembly and arranged in contra-rotational relationship to each other. The pitch control mechanism includes an actuator assembly configured to be secured to a non-rotating frame of the engine, the actuator assembly having a first actuator and a second actuator, with the actuator assembly being rotationally isolatable from and couplable to the first and second rotor assemblies such that, in use, an actuation signal from the first or second actuator induces a corresponding desired change in pitch of the airfoil blades of the respective first or second rotor assembly independently of the pitch of the airfoil blades of the second or first rotor assembly.

What is claimed is: 
     
         1 - 11 . (canceled) 
     
     
         12 . An actuator assembly, comprising:
 a first actuator coupled to a first rotor assembly of a turbine engine, wherein the first rotor assembly includes a first set of airfoil blades mounted circumferentially on the first rotor assembly;   a second actuator coupled to a second rotor assembly of the turbine engine, wherein the second rotor assembly includes a second set of airfoil blades mounted circumferentially on the second rotor assembly, and the second set of airfoil blades are arranged in contra-rotational relationship with the first set of airfoil blades;   wherein the actuator assembly is configured to be secured to a non-rotating frame of the turbine engine, rotationally isolated from the first and second rotor assemblies, spatially decoupled from a gearbox configured to transfer rotational drive to at least one of the first or second rotor assemblies, and an actuation signal from the first actuator induces a corresponding change in pitch of the first set of airfoil blades independently of the pitch of the second set of airfoil blades.   
     
     
         13 . The actuator assembly of  claim 12 , wherein an actuation signal from the second actuator induces a corresponding change in pitch of the second set of airfoil blades independently of the pitch of the first set of airfoil blades. 
     
     
         14 . The actuator assembly of  claim 13 , wherein the first and second actuators are concentrically mounted. 
     
     
         15 . The actuator assembly of  claim 12 , wherein the actuator assembly is rotationally isolated from the first and second rotor assemblies via a set of bearing arrangements. 
     
     
         16 . The actuator assembly of  claim 15 , wherein the first actuator is coupled to the first rotor assembly via a first bearing arrangement included in the set of bearing arrangements. 
     
     
         17 . The actuator assembly of  claim 16 , wherein the first bearing arrangement is configured to transmit a displacement signal of the first actuator to the first rotor assembly, and is coupled to the first set of airfoil blades, wherein the displacement signal is converted to a rotational output signal to adjust the pitch of the first set of airfoil blades. 
     
     
         18 . The actuator assembly of  claim 17 , further comprising a pin and roller arrangement for coupling the first bearing arrangement with the first set of airfoil blades. 
     
     
         19 . The actuator assembly of  claim 18 , wherein the first bearing arrangement includes a bearing mounted relative to the first actuator such that the displacement signal of the first actuator acts upon an axial end face of the bearing to transmit a corresponding axial load to an axially slideable annular yoke rotatable with the respective first rotor assembly, the airfoil blades of the first rotor assembly being mounted to a plurality of radially extending shafts circumferentially disposed about the yoke, the pin and roller arrangement includes:
 a combination of a pin and a roller associated with at least one of the radially extending shafts,   wherein the roller is located in an annular groove provided on a surface of the yoke, the roller is configured to slide about the annular groove of the yoke under the action of the transmitted axial load, and the roller is offset from a longitudinal axis of the associated at least one radially extending shafts, and   wherein the pin connects each roller to the associated at least one radially extending shafts such that sliding of the roller about the annular groove of the yoke acts upon the pin to twist the associated at least one radially extending shafts and thereby adjust the pitch of the first set of airfoil blades.   
     
     
         20 . The actuator assembly of  claim 19 , wherein each shaft of the plurality of radially extending shafts is associated to a respective combination of pin and roller. 
     
     
         21 . The actuator assembly of  claim 20 , wherein the actuator assembly is mounted along or parallel to a longitudinal axis of the turbine engine. 
     
     
         22 . The actuator assembly of  claim 12 , wherein the gearbox is an epicyclic gearbox for transferring rotational drive to both of the first and second rotor assemblies, the first and second rotor assemblies being driven in opposing directions.