Pitch change signal means with differential gearing

Claim 2

For a fan or propeller having variable pitch blades and means including a gearbox having a train of gears for reducing the speed of the fan or propeller from its driving means, pitch change means including a rotary actuator for changing the blade angle of the blades, the improvement comprising a differential gear set operatively connected to said rotary actuator consisting of a sun gear, one set of planetary gears and a ring gear connected to said rotary actuator, said sun gear being grounded to a rotating member of said gearbox, said differential gear set having the same gear ratio as the ratio of the train of gears of said gearbox, a cage supporting said set of planetary gears and movable to add to or substract from the rotational speed of said ring gear, means interconnecting said blades and said rotary actuator for imparting pitch change movement in response to said added or substracted speed, and means for imparting movement to said cage in accordance with a desired blade angle.

Claim 3

For a fan or propeller as claimed in claim 1 wherein said rotary actuator is a harmonic drive.

Claim 4

For a fan or propeller as claimed in claim 2 including a hub supporting said blades, said harmonic drive including a spline member connected to said hub and another spline member connected to said blade.

Claim 5

In combination, a variable pitch propeller or fan driven by a power plant, a hub supporting a plurality of blades for pitch change movement, gear reduction means between the power plant and propeller or fan drivingly connected to said hub to rotate it at a speed less than that of the power plant, said gear reduction means including a first sun gear, a first ring gear, and a first set of planetary gears, said first ring gear being connected to said hub, rotary actuation means being grounded to said hub for rotation at the same speed thereof, means for actuating said rotary actuation means from a stationary location remote from said hub for changing the blade angle of the blades in accordance to a desired blade angle setting, said means including a differential gear set consisting of a second sun gear grounded to said first sun gear, a second ring gear operatively connected to said rotary actuator, and a second set of planetary gears, a cage rotary supporting said planetary gears and means for imparting movement to said cage for changing the relative speed of said differential gear set for effectuating pitch change movement.

Claim 6

In combination, a variable pitch propeller or fan driven by a power plant, a hub supporting a plurality of blades for pitch change movement, gear reduction means between the power plant and propeller or fan drivingly connected to said hub to rotate it at a speed less than that of the power plant, said gear reduction means including a first sun gear, a first ring gear, and a first set of planetary gears, said first ring gear being connected to said hub, rotary actuation means being grounded to said hub for rotation at the same speed thereof, means for actuating said rotary actuation means from a stationary location remote from said hub for changing the blade angle of the blades in accordance to a desired blade angle setting, said means including a differential gear set consisting of a second sun gear grounded to said first sun gear, a second ring gear operatively connected to said rotary actuator, and a second set of planetary gears, a cage rotary supporting said planetary gears and means for imparting movement to said cage for changing the relative speed of said differential gear set for effectuating pitch change movement.

Claim 7

The combination as claimed in claim 4 wherein said rotary actuator includes a harmonic drive having a rigid spline connected to said blade for changing the blade angle thereof, a flexible spline drivingly connected thereto connected to said hub for rotating at the same speed thereof, and a motion generator driven by said second ring gear, whereby rotation of said cage increases and reduces the relative speed of said differential gear set with respect to said hub for effectuating pitch change movement.