Cyclic pitch actuation system for counter-rotating propellers

Abstract

A counter-rotating propeller system comprises a cyclic pitch system connected to a first plurality of propeller blades and a variable pitch system connected to a second plurality of propeller blades. The first plurality of propeller blades and the second plurality of propeller blades are configured to rotate about a common axis.

What is claimed is: 
     
         1 . A counter-rotating propeller system comprising:
 a cyclic pitch system connected to a first plurality of propeller blades; and   a variable pitch system connected to a second plurality of propeller blades, wherein the first plurality of propeller blades and the second plurality of propeller blades are configured to rotate about a common axis.   
     
     
         2 . The system of  claim 1 , further comprising a first hub supporting the first plurality of propeller blades, the first hub supported for rotation directly by a first input shaft such that the first hub is rotatable relative to the first input shaft. 
     
     
         3 . The system of  claim 2 , further comprising a second input shaft supported by the first hub for rotation relative to the first hub and the first input shaft. 
     
     
         4 . The system of  claim 3 , further comprising a second hub supporting the second plurality of propeller blades, the second hub supported by the second input shaft. 
     
     
         5 . The system of  claim 4 , further comprising a planetary gear train driven by the first input shaft, the planetary gear train including a sun gear attached for rotation with the first input shaft, at least one planet gear supported on a planet gear carrier attached to the second input shaft, and a ring gear defined by the first hub, wherein the planetary gear train drives the first hub in a first direction and the second hub in a second direction opposite the first direction. 
     
     
         6 . The system of  claim 1 , wherein the cyclic pitch system includes a plurality of actuators configured to vary a pitch between at least two of the first plurality of propeller blades. 
     
     
         7 . The system of  claim 6 , wherein the cyclic pitch system includes a first hoop rotatably engaging a second hoop. 
     
     
         8 . The system of  claim 7 , wherein the first hoop is non-rotational and attached to the plurality of actuators and the second hoop rotates with the first plurality of propeller blades. 
     
     
         9 . The system of  claim 8 , wherein the first hoop is attached to the plurality of actuators with a spherical joint. 
     
     
         10 . The system of  claim 1 , wherein the variable pitch system includes an actuator disposed in a second hub configured to adjust a pitch of the second plurality of propeller blades. 
     
     
         11 . A method of controlling a counter-rotating propeller system comprising:
 cyclically changing a pitch of a first plurality of propeller blades with a cyclic pitch system; and   variably changing a pitch of a second plurality of propeller blades with a variable pitch system.   
     
     
         12 . The method of  claim 11 , wherein the pitch of the first plurality of propeller blades varies depending on a circumferential location of each of the first plurality of propeller blades. 
     
     
         13 . The method of  claim 12 , wherein the pitch of the second plurality of propeller blades is varied approximately equally. 
     
     
         14 . The method of  claim 11 , wherein the cyclic pitch system includes a first hoop rotatably engaging a second hoop and the first hoop is non-rotational and attached to a plurality of actuators and the second hoop rotates with the first plurality of propeller blades. 
     
     
         15 . The method of  claim 14 , wherein the variable pitch system includes an actuator disposed in a hub configured to adjust a pitch of the second plurality of propeller blades.