Multiple-stage geared rotary actuator

Abstract

A multiple-stage geared rotary actuator having a plurality of balanced compound differentials providing a multiple-stage output and for converting a high-speed, low-torque input to a low-speed, high-torque output for moving a member, such as an aircraft flight control surface. The balanced compound planetary differentials each have a plurality of planet gear shafts with a center gear and outer gears at opposite sides of the center gear and with the tubular planet gear shafts of the planetary differentials being in axial alignment. The maximum deflection resulting from bending forces acting on the tubular planet gear shafts is minimized by changing the boundary conditions at the ends of the planet gear shafts. This change in the boundary conditions is achieved by the use of structure positioned within the planetary gear shafts and extending through the length of the rotary gear actuator and common to all of the axially aligned tubular gear shafts, with one embodiment of such support structure being a bolt which preloads the adjacent tubular planet gear shafts. The support of the tubular planet gear shafts enables the design of a geared rotary actuator using longer planet gear shafts for increased torque-transmitting capability while keeping planet gear shaft deflections within acceptable limits for optimum gear mesh.