Projectile Fin Blocking With Spring-Loaded Ball Ramp Locking
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Solution Overview
Problem
Existing fin blocking devices for projectiles are unreliable and unstable, particularly when fins pivot about an axis parallel to the projectile, leading to partial retraction and oscillation issues, which affect the stability and range of the projectile.
Innovation Solution
A device featuring a recess with a shape of revolution, such as a roller or ball, pushed by resilient means, including an undulating leaf spring, which ensures constant contact with a ramp surface, preventing fin folding by balancing forces to maintain the fin in the deployed position, suitable for both parallel and perpendicular pivot axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a blade is used to block the fin during deployment (as in patent FR 2,895,071), then the fin can be prevented from folding, but the bracing is not always perfectly and quickly obtained, causing partial retraction of the fin
Solution Approach 1:
The patent replaces the blade with a ball (spherical element) that interacts with a ramp surface. The ball is pushed by a spring against the ramp, creating a jamming mechanism that is more reliable and quicker than blade bracing. The curved geometry of the ball and ramp ensures positive engagement and prevents fin retraction more effectively.
Solution Approach 2:
The ball acts as an intermediary element between the fin base and the projectile body. Instead of direct blade-to-fin contact, the ball mediates the blocking action by being pressed against the ramp surface, providing a more reliable and controlled blocking mechanism that quickly prevents fin folding.
2Reliability
If a ball in a groove with spring pushing is used (as in patent U.S. Pat. No. 4,143,838), then the fin can be blocked during retraction, but the radial pushing does not guarantee rigid locking, leading to oscillation and instability
Solution Approach 1:
The patent uses a ball (spherical element) in conjunction with a ramp surface to create a jamming mechanism. The curved geometry of the ball interacting with the inclined ramp provides rigid locking in the deployed position, preventing oscillation and instability that occur with simple radial spring pushing.
Solution Approach 2:
The spring is pre-loaded to push the ball against the ramp surface before fin deployment. This preliminary positioning of the ball against the ramp creates a pre-tensioned blocking mechanism that immediately prevents fin oscillation and rebound when the fin is deployed, rather than relying on radial pushing alone.
3Reliability
If a weight that slides below the fin base is used (as in patent FR 3,037,390), then the fin can be kept retracted during acceleration, but the device is complex and requires an inertial weight that must return to ensure blocking
Solution Approach 1:
The patent extracts the complex inertial weight mechanism and replaces it with a simpler ball-and-ramp system. The ball, pushed by a spring against a ramp surface, provides reliable blocking without requiring separate inertial weights that must slide and return. This simplifies the device while maintaining or improving blocking reliability.
Solution Approach 2:
The spring-loaded ball mechanism is self-actuating and does not require external inertial weights or complex return mechanisms. The spring automatically positions the ball against the ramp to block the fin, and the geometry of the ramp ensures the ball remains in place during flight, making the system self-sufficient and simpler than weight-based solutions.
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 reliable and consistent fin blocking, ensuring stability and range optimization by preventing fin retraction and oscillation, enhancing the projectile's flight performance.
Implementation Method 1
pushed by a resilient means between a first surface borne by the fin and a second surface borne by the body of the projectile
Implementation Method 2
the resilient means includes an undulating leaf spring placed along the roller
Implementation Method 3
at least one of the two surfaces forming a ramp that converges toward the other surface to tend to cause jamming of the shape of revolution between the two surfaces
Data Source
AI summary
A device for blocking a fin of a projectile, the fin including a fin base pivoting about a pivot pin secured to the body of the projectile between a withdrawn fin position and a deployed fin position, wherein the device includes at least one recess housing at least one shape of revolution pushed by a resilient means between a first surface borne by the fin and a second surface borne by the body of the projectile, at least one of the two surfaces forming a ramp that converges toward the other surface to tend to cause jamming of the shape of revolution between the two surfaces.