Articulated rotor systems with pitch independent damping

• US 10,457,380 B2
• Filed: 06/28/2017
• Issued: 10/29/2019
• Est. Priority Date: 06/28/2017
• Status: Active Grant

• Current Assignee: Bell Helicopter Textron Incorporated (Textron Inc)
• Original Assignee: Bell Textron Inc.
• Inventors: Choi, Jouyoung Jason, Parham, Jr., Thomas Clement, Miller, Gary, Stamps, Frank Bradley
• Primary Examiner(s): Benedik, Justin M
• Application Number:
  US15/636,448
• Publication Number:
  US 20190002085A1
• Time in Patent Office: 853 Days
• CPC Class Codes: B64C 11/06 for variable-pitch blades
• CPC Class Codes: B64C 11/32 mechanical
• CPC Class Codes: B64C 27/35 having elastomeric joints
• CPC Class Codes: B64C 27/51 Damping of blade movements
• CPC Class Codes: B64C 27/635 specially for controlling lag-lead movements of blades
• CPC Class Codes: B64C 29/0033 the propellers being tiltable relative to the fuselage
• CPC Class Codes: F16C 23/043 with spherical surfaces, e.g. spherical plain bearings
• CPC Class Codes: F16C 2326/43 Aeroplanes; Helicopters in general B64C
• CPC Class Codes: F16C 27/02 Sliding-contact bearings
• CPC Class Codes: F16F 15/1208 Bearing arrangements
• CPC Class Codes: F16F 15/121 using springs as elastic members, e.g. metallic springs F16F15/133 takes precedence
• CPC Class Codes: F16F 15/124 Elastomeric springs F16F15/123, F16F15/127 take precedence

Abstract

A proprotor system operable for use on a tiltrotor aircraft having a helicopter flight mode and an airplane flight mode. The proprotor system includes a rotor hub and a plurality of proprotor blades coupled to the rotor hub such that each proprotor blade has three independent degrees of freedom relative to the rotor hub including blade pitch about a pitch change axis, blade flap about a flapping axis and lead-lag about a lead-lag axis. Each of a plurality of spherical bearings couples one of the proprotor blades with the rotor hub. In addition, each of a plurality of lead-lag dampers couples one of the proprotor blades with the rotor hub, wherein each lead-lag damper is aligned with the pitch change axis of the respective proprotor blade, thereby providing pitch independent lead-lag damping.

Claims

1. A proprotor system operable for use on a tiltrotor aircraft having a helicopter flight mode and an airplane flight mode, the proprotor system comprising:

a rotor hub;

a plurality of proprotor blades coupled to the rotor hub such that each proprotor blade has three independent degrees of freedom relative to the rotor hub including blade pitch about a pitch change axis, blade flap about a flapping axis and lead-lag about a lead-lag axis;

a plurality of twin spherical elastomeric centrifugal force bearings each coupling one of the proprotor blades with the rotor hub and each providing a coincident hinge with a center point for the respective pitch change, flapping and lead-lag axes between a pair of oppositely disposed spherical surfaces; and

a plurality of lead-lag dampers each coupling one of the proprotor blades with the rotor hub, each lead-lag damper aligned with the pitch change axis of the respective proprotor blade, thereby providing pitch independent lead-lag damping.

2. The proprotor system as recited in claim 1 wherein each lead-lag damper further comprises an in-plane spring rate that is independent of blade pitch.

3. The proprotor system as recited in claim 1 wherein each lead-lag damper is disposed outboard of the respective spherical bearing.

4. The proprotor system as recited in claim 1 wherein each lead-lag damper is disposed inboard of the respective spherical bearing.

5. The proprotor system as recited in claim 1 wherein each lead-lag damper further comprises a damping cylinder coaxially aligned with the pitch change axis of the respective proprotor blade, a damping support coupled to the rotor hub and a damping link coupling the damping cylinder to the damping support, the damping link coupled to the damping support inline with the flapping axis of the respective proprotor blade.

6. The proprotor system as recited in claim 5 wherein each damping cylinder further comprises a mechanical spring having an in-plane spring rate operable to provide lead-lag damping to the respective proprotor blade.

7. The proprotor system as recited in claim 5 wherein each damping cylinder further comprises a fluid spring having an in-plane spring rate operable to provide lead-lag damping to the respective proprotor blade.

8. The proprotor system as recited in claim 5 wherein each damping cylinder further comprises a mechanical spring in combination with a fluid spring having an in-plane spring rate operable to provide lead-lag damping to the respective proprotor blade.

9. The proprotor system as recited in claim 5 wherein at least a portion of each damping cylinder is operable to rotate about the pitch change axis of the respective proprotor blade responsive to a change in pitch of the respective proprotor blade.

10. The proprotor system as recited in claim 1 wherein each lead-lag damper further comprises an elastomeric damping element coupled to the rotor hub and a damping link coupling the respective proprotor blade to the elastomeric damping element, the damping link having a first rotary bearing coaxially aligned with the pitch change axis of the respective proprotor blade and a second rotary bearing coupled to the elastomeric damping element.

11. The proprotor system as recited in claim 1 further comprising a plurality of blade anchors each coupling one of the spherical bearings with the rotor hub.

12. The proprotor system as recited in claim 1 further comprising a plurality of blade grips each coupling one of the spherical bearings with the respective proprotor blade.

13. The proprotor system as recited in claim 12 wherein each blade grip further comprises a pitch horn operable to receive collective input from a pitch control assembly.

14. The proprotor system as recited in claim 12 wherein each blade grip further comprises a pitch horn operable to receive cyclic input from a pitch control assembly.

15. A tiltrotor aircraft having a helicopter flight mode and an airplane flight mode, the tiltrotor aircraft comprising:

a fuselage;

a wing extending from the fuselage having first and second outboard ends;

first and second pylon assemblies respectively coupled to the wing proximate the first and second outboard ends; and

a proprotor system operably associated with each pylon assembly, each proprotor system including;

a rotor hub;

a plurality of proprotor blades coupled to the rotor hub such that each proprotor blade has three independent degrees of freedom relative to the rotor hub including blade pitch about a pitch change axis, blade flap about a flapping axis and lead-lag about a lead-lag axis;

a plurality of twin spherical elastomeric centrifugal force bearings each coupling one of the proprotor blades with the rotor hub and each providing a coincident hinge with a center point for the respective pitch change, flapping and lead-lag axes between a pair of oppositely disposed spherical surfaces; and

a plurality of lead-lag dampers each coupling one of the proprotor blades with the rotor hub, each lead-lag damper aligned with the pitch change axis of the respective proprotor blade, thereby providing pitch independent lead-lag damping.

16. The tiltrotor aircraft as recited in claim 15 wherein each lead-lag damper further comprises an in-plane spring rate that is independent of blade pitch.

17. The tiltrotor aircraft as recited in claim 15 wherein each lead-lag damper further comprises a damping cylinder coaxially aligned with the pitch change axis of the respective proprotor blade, a damping support coupled to the rotor hub and a damping link coupling the damping cylinder to the damping support, the damping link coupled to the damping support inline with the flapping axis of the respective proprotor blade.

18. The tiltrotor aircraft as recited in claim 17 wherein each damping cylinder further comprises a spring having an in-plane spring rate operable to provide lead-lag damping to the respective proprotor blade, the spring selected from the group consisting of a mechanical spring, a fluid spring and combinations thereof.

19. The tiltrotor aircraft as recited in claim 15 wherein each lead-lag damper further comprises an elastomeric damping element coupled to the rotor hub and a damping link coupling the respective proprotor blade to the elastomeric damping element, the damping link having a first rotary bearing coaxially aligned with the pitch change axis of the respective proprotor blade and a second rotary bearing coupled to the elastomeric damping element.

20. The tiltrotor aircraft as recited in claim 15 further comprising a plurality of blade grips each coupling one of the spherical bearings with the respective proprotor blade, each blade grip including a pitch horn operable to receive at least one of collective input and cyclic input from a pitch control assembly.