Drive system for a variable diameter tilt rotor

A rotor hub assembly for a variable diameter rotor system, the system including a plurality of rotor blade assemblies mounted to and rotated by the rotor hub assembly about an axis of rotation, each rotor blade assembly having an inboard blade section and an outboard blade section, the outboard blade section being telescopically mounted to the inboard blade section, each rotor blade assembly having a mass center, the system further including a jackscrew rotatably disposed within the rotor blade assembly and engaged with the outboard blade section for telescoping the outboard blade section with respect to the inboard blade section, the jackscrew having an output pinion located at its inboard end, the rotor hub assembly comprising:

• a main rotor shaft having an upper end and an axis of rotation;
• a rotor hub disposed about the upper end of the main rotor shaft, the blade assemblies being spaced about and attached to the rotor hub, the rotor hub having a pivot point located at the intersection of the axis of rotation and a line along the mass center of the rotor blade assemblies;
• a first elastomeric bearing disposed between and attached to the upper end of the main rotor shaft and the rotor hub;
• a second elastomeric bearing attached to the main rotor shaft and the rotor hub and located above the upper end of the rotor shaft;
• the first and second elastomeric bearings each having a substantially spherical shape and centers of curvature that substantially coincide with one another and the rotor hub pivot point at a location between the first and second elastomeric bearings;
• a blade actuation shaft concentrically disposed within the main rotor shaft, the blade actuation shaft having an upper end;
• a constant velocity joint pivotally attached to the upper end of the blade actuation shaft about the pivot point;
• and
• a planetary gearset located within the rotor hub assembly including
• a sun gear attached to a housing above the second elastomeric bearing,
• a plurality of pinion gears disposed about and intermeshing with the sun gear, the pinion gears being rotatably mounted to a pinion cage, the pinion cage being rotatably in contact with the rotor hub,
• a lower hypoid bevel gear attached to the pinion gears and forms a ring within the rotor hub assembly, the lower hypoid bevel gear adapted to intermesh with the output pinion on the jackscrew, and
• a ring gear located radially outward from and intermeshing with the pinion gears.

A variable diameter rotor system for an aircraft comprising

• a main rotor shaft having an upper end and having an axis of rotation;
• a plurality of rotor blade assemblies, each rotor blade assembly having an inner blade segment and an outer blade segment, the outer blade segment being telescopically mounted to the inner blade segment, each rotor blade assembly having a mass center;
• a jackscrew rotatably disposed within the rotor blade assembly and engaged with the outer blade segment for telescoping the outer blade segment with respect to the inner blade segment, the jackscrew having an output pinion located at its inboard end,
• a rotor hub having an axis of rotation and being pivotally mounted to the upper end of the main rotor shaft about a pivot point, the pivot point being located at the intersection of the rotor hub axis of rotation and a line along the mass center of the rotor blade assemblies, the inner blade segment of each rotor blade assembly being mounted to the rotor hub assembly such that the rotor blade assemblies are rotated by the rotor hub assembly about the rotor hub axis of rotation;
• a first elastomeric bearing disposed between and attached to an upper portion of the main rotor shaft and the rotor hub;
• a second elastomeric bearing attached to the main rotor shaft and the rotor hub;
• the first and second elastomeric bearings permitting pivoting of the rotor hub about the pivot point with respect to the main rotor shaft while transmitting rotational loads therebetween;
• a blade actuation shaft concentrically disposed within the main rotor shaft, the blade actuation shaft having an upper end;
• a constant velocity joint pivotally attached to the upper end of the blade actuation shaft about the pivot point;
• and
• a planetary gearset located within the rotor hub and engaging the blade actuation shaft with the output pinion, the planetary gearset including
• a sun gear attached to a housing above the second elastomeric bearing,
• a fixed ring gear attached to the rotor hub and located radially out board from the sun gear, and
• a plurality of pinion gears disposed between and intermeshing with the sun gear and the ring gear, the pinion gears being rotatably mounted to a pinion cage, the pinion cage being rotatable with respect to the housing and the fixed ring gear,
• a lower hypoid bevel gear rotatably driven by the pinion gears and adapted to intermesh with the output pinion on the jackscrew.