Spherical Bearing Assembly With Shim-Controlled Break-Away Torque
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Solution Overview
Problem
Conventional bearing assemblies for helicopter main rotor actuators require a narrow range of tightening torque to achieve an acceptable break-away torque, leading to frequent adjustments and reduced stability under varying external loads, and increasing the torque results in excessively high break-away torque.
Innovation Solution
A bearing assembly with a shim between the outer races, allowing a primary load path that bypasses the spherical bearing, enabling higher tightening torque without excessively increasing break-away torque, and a method to maintain the acceptable range of break-away torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the tightening torque is increased to achieve higher stability under varying external loads, then the stability is improved, but the break-away torque becomes excessively high
Solution Approach 1:
A shim is introduced as an intermediary component between the outer races. The shim absorbs excess tightening force through deformation, acting as a mediator that prevents the full tightening torque from being transmitted to the spherical bearing. This allows the outer nut to be tightened to a higher torque for stability while the shim limits the break-away torque to an acceptable range.
Solution Approach 2:
The shim changes its physical state from a rigid spacer to a deformed element under load. By selecting appropriate shim material properties and initial dimensions, the shim's deformation characteristics are designed to absorb a specific range of tightening forces, thereby controlling the break-away torque parameter independently of the tightening torque applied.
2Duration of action of moving object
If the tightening torque is increased to reduce maintenance frequency, then the duration of action is improved, but the break-away torque becomes excessively high requiring adjustment
Solution Approach 1:
The shim serves as a maintenance-free intermediary that permanently absorbs the excess tightening force. Once the outer nut is tightened to the optimal torque, the shim deforms to maintain this force level, preventing both over-tightening and under-tightening issues that would otherwise require periodic adjustment.
Solution Approach 2:
The shim performs a self-regulating function by automatically deforming to absorb excess tightening force. This self-service mechanism eliminates the need for periodic monitoring and adjustment of the bearing assembly, extending the maintenance interval without requiring the break-away torque to be excessively high.
3Ease of operation
If additional liners are added to reduce friction and maintain smooth operation, then the ease of operation is improved, but the device complexity increases and ground resonance issues occur
Solution Approach 1:
The patent removes the additional liners that were previously added to reduce friction. Instead, the friction characteristics are optimized through the shim design and proper tightening torque control, eliminating the need for extra friction-reducing components and avoiding the ground resonance issues they caused.
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
The solution provides a bearing assembly that can withstand higher external forces with reduced maintenance needs, maintaining stability and break-away torque within acceptable limits, and eliminates the need for additional liners, thus preventing ground resonance issues in helicopters.
Implementation Method 1
The shim is configured to absorb some of the tightening force in use
Implementation Method 2
The outer nut is configured to tighten onto the housing and apply a load to the shim through the outer races
Implementation Method 3
The outer races are configured in sliding engagement with the spherical bearing to allow the spherical bearing to rotate relative to the housing
Data Source
AI summary
A bearing assembly includes a housing, a spherical bearing located within the housing, and two outer races positioned between the spherical bearing and the housing. The outer races are configured in sliding engagement with the spherical bearing to allow the spherical bearing to rotate relative to the housing. The assembly also includes a tightening element configured to engage a first of the two outer races and tighten the outer races against the spherical bearing. The assembly is configured to provide a primary load path from the tightening element to the housing, wherein the primary load path leads from the tightening element to the housing via the outer races whilst bypassing the spherical bearing.