Passive rotor pitch control system

Patent metadata

Field	Value
Publication number	US-12162585-B2
Application number	US-202318185628-A
Country	US
Kind code	B2
Filing date	Mar 17, 2023
Priority date	Mar 17, 2023
Publication date	Dec 10, 2024
Grant date	Dec 10, 2024

Abstract

One example includes a passive rotor pitch control system. The system includes a counterweights that are each associated with one of a respective plurality of rotors and can be arranged to have a center of mass configured to provide a pitch torque about a pitch axis associated with the respective one of the rotors in response to rotation of the rotors about a rotation axis. The system also includes a spring forcer comprising a pitch rod and a spring configured to provide a spring force on the pitch rod. The system further includes a pitch change assembly coupled to the counterweights and the pitch rod. The pitch change assembly can be configured to rotate a pitch of each of the rotors from a first pitch state to a second pitch state in response to a sum of pitch torques associated with the counterweights being greater than the spring force.

First claim

What is claimed is:

1. A passive rotor pitch control system comprising:
a plurality of counterweights, each of the counterweights being associated with one of a respective plurality of rotors and being arranged to have a center of mass configured to provide a pitch torque about a pitch axis associated with the respective one of the rotors in response to rotation of the rotors about a rotation axis;
a spring forcer comprising a pitch rod and a spring configured to provide a spring force on the pitch rod; and
a pitch change assembly coupled to the counterweights and comprising a scotch yoke mechanism coupled to the pitch rod, the scotch yoke mechanism providing an axial force on the pitch rod opposite the spring force in response to a sum of the pitch torques associated with the counterweights, the pitch change assembly being configured to rotate a pitch of each of the rotors from a first pitch state to a second pitch state in response to the axial force being greater than the spring force.

2. The system of claim 1 , wherein the counterweights comprise a pair of counterweights associated with a respective pair of rotors, wherein the pitch rod is arranged along a first axis corresponding to the rotation axis about which the rotors rotate and along which the spring force is provided, wherein the scotch yoke mechanism comprises:
a yoke coupled to the pitch rod, the yoke comprising a planar yoke surface arranged orthogonal with respect to the first axis;
a slider block that is associated with one of the rotors and configured to slide against and push on the planar yoke surface; and
a slider pin coupled to one of the rotors and extending through the slider block along an axis parallel to the pitch axis, such that, in response to the sum of the pitch torques associated with the counterweights being greater than the spring force, the slider pin rotates about the pitch axis to slide the slider pin along the planar yoke surface to provide the axial force on the planar yoke surface along the first axis opposite the spring force.

3. The system of claim 2 , wherein the yoke comprises a pair of planar yoke surfaces arranged orthogonal with respect to the first axis;
wherein the slider block is a first of a pair of slider blocks that are each associated with one of the rotors and configured to slide against and push on the respective pair of planar yoke surfaces; and
wherein the slider pin is a first of a pair of slider pins coupled to a respective one of the rotors through the respective one of the slider blocks along respective axes parallel to the pitch axis, such that, in response to the sum of the pitch torques associated with the counterweights being greater than the spring force, the slider pins each rotate about the pitch axis to slide the respective one of the slider pins along the respective one of the planar yoke surfaces to provide the axial force on the planar yoke surface along the first axis opposite the spring force.

4. The system of claim 1 , wherein the counterweights comprise a set of counterweights associated with a respective set of rotors greater than two, wherein the scotch yoke mechanism comprises:
a yoke coupled to the pitch rod, the yoke comprising a housing enclosing the pitch rod and further comprising a first rotating joint arranged exterior to the housing; and
a pitch arm coupled at a first end to the first rotating joint and coupled at a second end to one of the counterweights via a second rotating joint, wherein the pitch torque provided by the respective one of the counterweights is provided along the pitch arm via the second rotating joint, such that the pitch arm provides a component of the axial force on the pitch rod opposite the spring force via the first rotating joint on the housing.

5. The system of claim 4 , wherein the first rotating joint is a first of a plurality of first rotating joints arranged exterior to the housing;
wherein the pitch arm is a first of a plurality of pitch arms, each of the pitch arms coupled at a first end to one of the first rotating joints and coupled at a second end to a respective one of the counterweights via one of a plurality of second rotating joints, wherein the pitch torque provided by each of the counterweights is provided along the respective one of the pitch arms via the respective one of the second rotating joints, such that the pitch arms each provide a respective component of the axial force on the pitch rod opposite the spring force via the respective one of the first rotating joints on the housing.

6. The system of claim 1 , wherein the spring forcer further comprises:
a forcer housing enclosing the spring and at least a portion of pitch rod and being filled with a viscous fluid; and
a dividing disk formed integral with and about the pitch rod, the dividing disk dividing an interior of the forcer housing into a first portion and a second portion, the dividing disk comprising at least one through-hole to provide flow-through of the viscous fluid to facilitate a slow transition between the first pitch state and the second pitch state.

7. The system of claim 1 , wherein the spring force of the spring is selected to provide a threshold angular velocity of the rotors at which the sum of the pitch torques associated with the counterweights becomes greater than the spring force to facilitate a transition from the first pitch state to the second pitch state.

8. The system of claim 1 , wherein the first pitch state corresponds to a first pitch and a first angular velocity of the rotors and the second pitch state corresponds to a second pitch and a second angular velocity of the rotors, wherein the first pitch is greater than the second pitch, wherein the second angular velocity is greater than the first angular velocity.

9. A vertical takeoff and landing (VTOL) vehicle comprising the rotors and the passive rotor pitch control system of claim 8 , wherein the first pitch state corresponds to horizontal flight of the VTOL vehicle via the rotors, wherein the second pitch state corresponds to takeoff, landing, and hover conditions of the VTOL vehicle via the rotors.

10. A method for operating a vertical takeoff and landing (VTOL) vehicle comprising a rotor assembly that includes a passive rotor pitch control system, the method comprising:
activating the rotor assembly to rotate to provide a pitch torque about a pitch axis associated with each of a plurality of rotors of the rotor assembly;
converting a sum of the pitch torques about each of the pitch axes into an axial force on a pitch rod via a scotch yoke mechanism coupled to the pitch rod;
increasing an angular velocity of rotation of the rotor assembly beyond a threshold angular velocity to increase the axial force greater than a spring force acting opposite the axial force on the pitch rod to rotate a pitch of each of the rotors from a first pitch state to a second pitch state via a pitch change assembly to provide lift of the VTOL vehicle for takeoff via the rotors; and
decreasing the angular velocity of rotation of the rotor assembly less than the threshold angular velocity to decrease the axial force less than the spring force on the pitch rod to rotate the pitch of each of the rotors from the second pitch state to the first pitch state via the pitch change assembly to provide horizontal flight of the VTOL vehicle via the rotors.

11. The method of claim 10 , wherein activating the rotors to rotate to provide the pitch torque comprises activating the rotors to rotate to provide the pitch torque via a plurality of counterweights that are each associated with a respective one of the rotors, each of the counterweights having a center of mass that provides the pitch torque about the

Assignees

• Loos Eric Stephen
• Fleming Jonathan Lee
• Gallman Judith Marie
• Talbert Robert Francis
• Northrop Grumman Systems Corp

Inventors

• Loos Eric Stephen
• Fleming Jonathan Lee
• Gallman Judith Marie
• Talbert Robert Francis

Classifications

• B64C29/02

  having its flight directional axis vertical when grounded · CPC title

• B64C11/346 Primary

  actuated by the centrifugal force or the aerodynamic drag acting on auxiliary masses or surfaces · CPC title