Variable pitch fan assembly with blade pitch indication

Abstract

A variable pitch fan assembly comprises a fan configured to rotate about a fan rotation axis and comprising blades with a pitch that is variable, a piston connected to the fan and configured to move axially relative to the fan rotation axis to change the pitch of the blades, a rotary crank arm yieldably biased toward the piston, and a motion transmitter positioned in communication with the piston and the crank arm to transmit motion axially therebetween relative to the fan rotation axis, and a sensor positioned to detect an angular position of the crank arm, the angular position indicative of the pitch of the blades.

What is claimed is: 
     
         1 . A variable pitch fan assembly, comprising:
 a fan configured to rotate about a fan rotation axis and comprising blades with a pitch that is variable,   a piston connected to the fan and configured to move axially relative to the fan rotation axis to change the pitch of the blades,   a rotary crank arm yieldably biased toward the piston,   a motion transmitter positioned in communication with the piston and the crank arm to transmit motion axially therebetween relative to the fan rotation axis, and   a sensor positioned to detect an angular position of the crank arm, the angular position indicative of the pitch of the blades.   
     
     
         2 . The variable pitch fan assembly of  claim 1 , comprising a bearing mounted to the motion transmitter, wherein the piston is connected to the motion transmitter via the bearing such that the piston is configured to rotate relative to the motion transmitter with the fan about the fan rotation axis. 
     
     
         3 . The variable pitch fan assembly of  claim 2 , comprising a spacer, wherein the bearing comprises an outer race and an inner race, and the spacer is supported on the outer race and spaces the piston apart from the inner race. 
     
     
         4 . The variable pitch fan assembly of  claim 3 , wherein the spacer contacts the bearing and the piston and comprises a ring surrounding the outer race and a lip extending radially from the ring relative to the fan rotation axis and axially between the bearing and the piston relative to the fan rotation axis so as to space the piston axially apart from the inner race relative to the fan rotation axis. 
     
     
         5 . The variable pitch fan assembly of  claim 2 , comprising a housing and a bushing positioned in a bore of the housing, wherein the motion transmitter is positioned in the bushing for axial and rotational movement relative to the fan rotational axis. 
     
     
         6 . The variable pitch fan assembly of  claim 1 , comprising a housing, wherein the fan is supported for rotation relative to the housing about the fan rotation axis, the housing comprises a cavity and a bore extending from the cavity, the crank arm is positioned in the cavity, and the motion transmitter is positioned in the bore for linear movement therein along the fan rotation axis. 
     
     
         7 . The variable pitch fan assembly of  claim 6 , comprising a bushing positioned in the bore, and the motion transmitter is positioned in the bushing. 
     
     
         8 . The variable pitch fan assembly of  claim 1 , wherein the motion transmitter and the crank arm are positioned in slidable contact with one another. 
     
     
         9 . The variable pitch fan assembly of  claim 1 , wherein the crank arm comprises a groove, and the motion transmitter comprises an end portion received in the groove. 
     
     
         10 . The variable pitch fan assembly of  claim 1 , wherein the motion transmitter and the crank arm cooperate to provide a spherical interface therebetween. 
     
     
         11 . The variable pitch fan assembly of  claim 10 , wherein the motion transmitter comprises a spherical end portion, and the crank arm comprises a spherical groove receiving the spherical end portion. 
     
     
         12 . The variable pitch fan assembly of  claim 11 , wherein the spherical groove extends lengthwise along a periphery of the crank arm. 
     
     
         13 . The variable pitch fan assembly of  claim 11 , wherein the crank arm is configured to rotate about a crank rotation axis, and the spherical groove lies in an imaginary plane perpendicular to the crank rotation axis. 
     
     
         14 . The variable pitch fan assembly of  claim 1 , wherein the motion transmitter is configured as a rod. 
     
     
         15 . The variable pitch fan assembly of  claim 1 , wherein the motion transmitter is positioned to transmit motion linearly between the piston and the crank arm.