Self-Retaining Anti-Rotation Key for Vibration-Resistant Fasteners
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Solution Overview
Problem
Existing anti-rotation keys in fastener assemblies, such as those used in rocket engine fuel pumps, often fail to securely prevent rotation of studs relative to housings due to vibration or thermal expansion, leading to potential disengagement and instability.
Innovation Solution
A self-retaining anti-rotation key design featuring a flex arm with a locking tip and angled surface, which is deflectable and biased towards a relaxed position, is inserted into a key channel, engaging with the stud and housing to prevent rotation and remain securely in place without the need for additional fastening, and can be easily removed when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional anti-rotation key is used in a fastener assembly, then the stud rotation is prevented initially, but the key may disengage due to vibration or thermal expansion
Solution Approach 1:
The anti-rotation key incorporates a resilient flex arm that can dynamically deflect between engaged and disengaged positions. This dynamic capability allows the key to maintain reliable engagement under normal conditions while adapting to vibrational and thermal changes, preventing disengagement that would occur with rigid traditional keys.
Solution Approach 2:
The flex arm's resilient properties enable parameter changes in the key's position and engagement force. By allowing the engagement parameters to vary dynamically rather than remaining fixed, the key maintains stable fastener assembly composition despite external disturbances like vibration and thermal expansion.
2Reliability
If a resilient flex arm with locking tip is used, then the anti-rotation key remains securely engaged despite vibrations and thermal changes, but the device complexity increases
Solution Approach 1:
The anti-rotation key utilizes a flexible thin film structure (the flex arm) that provides the necessary resilient engagement. This flexible structure achieves reliable retention under vibration and thermal changes while maintaining a relatively simple single-piece construction, avoiding the need for complex multi-component assemblies.
Solution Approach 2:
The flex arm's resilient nature enables self-service functionality where the key automatically maintains engagement through its own elastic properties. The locking tip engages and disengages automatically based on the deflection forces, eliminating the need for additional fastening mechanisms or complex control systems.
3Device complexity
If the anti-rotation key is securely retained without additional fastening, then the fastener assembly is simpler, but the key may become difficult to remove when necessary
Solution Approach 1:
The same dynamic resilient property that enables secure retention also facilitates easy removal. By applying sufficient force to deflect the flex arm beyond its engagement threshold, the locking tip disengages from the stud, allowing removal. This dynamic behavior provides both secure operation during use and ease of removal when needed, without requiring additional fastening or complex mechanisms.
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 self-retaining anti-rotation key effectively prevents stud rotation and remains securely engaged despite vibrations and thermal changes, ensuring stability in fastener assemblies, while allowing for easy removal when required.
Implementation Method 1
a flex arm with a locking tip and angled surface, which is deflectable and biased towards a relaxed position
Data Source
AI summary
Anti-rotation keys are typically used in applications where an end of a threaded stud is received in a housing, and where the opposite end of the stud projects from the housing to allow attachment of another component to the housing. Once partially received in the housing, further rotation of the stud is prevented by an anti-rotation key. The disclosed anti-rotation key is self-retaining, in that it prevents itself from “backing out” of the channel due to vibration or thermal expansion of the housing, etc., while also being removable from the channel if desired.