Rotation Rod Assembly with Grooved Bushings to Prevent Grease Bypass
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Solution Overview
Problem
Existing greased rotation rod assemblies for aircraft landing gear face issues with lubricant bypass and premature wear due to high friction and deformation under compressive forces, particularly when using self-lubricating polymers, which fail to provide adequate lubrication to all contact surfaces.
Innovation Solution
The implementation of a PTFE-lined rotation rod assembly with grooved bushings and debris reservoirs, where PTFE (polytetrafluoroethylene) self-lubricating liners are used to minimize friction and wear, and debris grooves are incorporated to collect and manage wear debris, ensuring consistent lubrication and reducing contact pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If self-lubricating polymers are used in place of metallic sleeves or bushings, then maintenance requirements are reduced, but the polymers fail under compressive forces and have high coefficient of friction
Solution Approach 1:
The patent uses a composite structure combining a metallic sleeve or bushing with an overlay layer of self-lubricating polymer material. The metallic substrate provides structural strength and compressive load-bearing capability, while the polymer overlay provides self-lubricating properties. This composite approach allows the bearing surface to withstand compressive forces while maintaining low friction and reducing maintenance requirements.
2Stress or pressure
If cylindrical bearing members with large surface areas are used, then contact pressures are reduced, but the coefficient of friction of polymers on aluminum alloys increases with decreasing contact pressure
Solution Approach 1:
The patent applies different material properties to different regions of the bearing surface. The metallic substrate provides the necessary contact pressure distribution, while the polymer overlay is applied selectively to the sliding contact surfaces where lubrication is needed. This localized application ensures that the polymer material operates in the optimal contact pressure range for low friction while the metallic structure maintains appropriate pressure distribution.
3Reliability
If grease is employed in the bore to reduce friction and wear, then lubrication is improved, but grease bypass occurs and periodic maintenance is still required
Solution Approach 1:
The self-lubricating polymer overlay provides inherent lubrication properties that do not require external grease supply or periodic replenishment. The polymer material contains lubricating additives that are released during operation, creating a self-sustaining lubrication film. This eliminates grease bypass issues and removes the need for periodic maintenance while maintaining effective lubrication throughout the service life of the component.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively prevents lubricant bypass and reduces wear by ensuring consistent grease distribution and managing debris, thereby extending the maintenance interval and improving the durability of the rotation rod assembly.
Implementation Method 1
PTFE (polytetrafluoroethylene) self-lubricating liners are used to minimize friction and wear
Implementation Method 2
grooved bushings configured to prevent bypass of grease flow
Data Source
Figure 1~3
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Figure 8~11
AI summary
A rotation rod assembly (100) includes a fixed member (120) having a first annular body portion (122) fixedly secured to and extending axially therefrom and a second annular body portion (124) having an inner surface (126) defining a first bore (128) axially extending partially into the second annular body portion, the second annular body portion having a first axial end and second axial end, the first axial end being closed and the second axial end having an opening with a plug (134) adjustably secured therein, the plug having a second bore extending therethrough, the first linkage rod being fixedly secured to a frame. The rotation rod assembly includes a rotatable member (140) having a piston section (142) extending axially therefrom, the piston section being coaxial with the rotatable member and the plug, the piston section being disposed for rotation in the first bore, the inner surface surrounding the piston section, the linkage arm (144) extending through the second bore and rotatable relative to the plug (134), the piston section being axially restrained by the first end and the plug (134); the piston section having a first bushing (141) and a second bushing (143) secured to at least one outer surface of the piston section (142), the first bushing (141) and the second bushing (143) having a lubrication groove (141X, 141Y, 143X, 143 Y) formed in an axially and a radially outer surface thereof, at least one of the first bushing (141) and the second bushing (143) being in sliding engagement with portions of the inner surface, the first end and a portion of the plug; a barrier for preventing flow of the grease inside the piston section; and a flow path for conveying grease around the piston section, the flow path comprising a first radial circuit in the first bushing, a first axial circuit in the first bushing, a second axial circuit around a radial outer surface of the piston section, a third axial circuit in the second bushing, and a second radial circuit in the second bushing.