Projectile Fin Adjustment Mechanism with Variable Backlash Gears
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Solution Overview
Problem
Existing projectile fin adjustment mechanisms with tight tolerances and stiff designs are costly to produce and prone to binding under high aerodynamic loads during flight, which can cause operational issues.
Innovation Solution
The adjustment mechanism incorporates a second gear with eccentric teeth that minimize backlash in the neutral fin position and increase backlash at larger steering angles, reducing the risk of binding due to higher aerodynamic loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tight tolerances and stiff designs are used in the adjustment mechanism, then manufacturing precision is improved, but the mechanism binds up under high aerodynamic loads during flight
Solution Approach 1:
The patent changes the backlash parameter dynamically through gear tooth geometry. The gear teeth are designed with varying backlash: minimal backlash at the neutral position for precision, and increased backlash at extreme positions to prevent binding under high aerodynamic loads. This parameter change resolves the contradiction by adapting the mechanical clearance to the operational state.
Solution Approach 2:
The adjustment mechanism transitions from a static, fixed-tolerance design to a dynamic system where backlash varies with gear position. The gear tooth profiles are specifically engineered to provide different clearances at different positions, allowing the mechanism to adapt to varying aerodynamic loads during flight while maintaining manufacturing precision where needed.
2Manufacturing precision
If tight tolerances are used in the adjustment mechanism, then manufacturing precision is improved, but production cost increases due to run-in and measurement requirements
Solution Approach 1:
The gear teeth are designed with intentional variable backlash that eliminates the need for post-manufacturing run-in procedures. The varying clearance is built into the gear geometry itself, allowing standard manufacturing processes to produce the final functional components without expensive precision running and measuring in multiple environments.
Solution Approach 2:
The gear design accepts that some clearance variation occurs during operation, but compensates for it through the built-in variable backlash geometry. This approach replaces expensive precision running and measurement processes with a simpler manufacturing method that incorporates tolerance compensation directly into the gear tooth profiles.
3Measurement precision
If minimal backlash is maintained in the adjustment mechanism, then control precision is improved, but the mechanism binds up under high aerodynamic loads at larger steering angles
Solution Approach 1:
The gear tooth profiles are specifically designed to provide minimal backlash at the neutral fin position for maximum control precision, while automatically increasing backlash at extreme steering angles. This dynamic parameter change prevents binding under high aerodynamic loads at extreme positions while maintaining precision control when the fin is in the neutral position.
Solution Approach 2:
Different parts of the gear engagement cycle have different quality requirements. The gear tooth geometry provides high precision (minimal backlash) locally at the neutral position where control precision is critical, and accepts greater clearance locally at extreme positions where binding prevention is more important. This local differentiation resolves the contradiction between precision and reliability.
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 design maintains control and reduces the likelihood of binding by providing necessary clearance as the fin adjusts, ensuring reliable operation under varying aerodynamic conditions while lowering production costs.
Implementation Method 1
The adjustment mechanism includes a first gear that engages the drive and a second gear that engages the fin and the first gear
Implementation Method 2
The second gear includes teeth that are different distances from an axis of rotation of the second gear
Data Source
AI summary
Some embodiments pertain to a projectile that includes a casing and at least one fin that extends from the casing. The projectile further includes a drive inside the casing and an adjustment mechanism inside the casing. The adjustment mechanism includes a first gear that engages the drive and a second gear that engages the fin and the first gear. The second gear includes teeth that are different distances from an axis of rotation of the second gear. The teeth of the second gear that engage the first gear may be the farthest from the axis of rotation of the second gear when the fin is aligned with a flight axis of the projectile. The engaging teeth of the second gear get closer to the axis of rotation of the second gear as the fin is maneuvered away from the flight axis of the projectile.