Inertial Igniter Delay Mechanism for Low-G Firing Detection
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Solution Overview
Problem
Existing mechanical inertial igniters face challenges in detecting low-g and long-duration firing accelerations, requiring compact size, high reliability, and safety from accidental activation, especially in munitions applications with low setback acceleration levels and extended durations, and are not suitable for small and miniaturized versions.
Innovation Solution
The design incorporates a striker mass mechanism with potential energy stored in a spring element, released upon detection of prescribed all-fire conditions, and includes a mechanical delay mechanism to ensure activation only under specific acceleration thresholds, minimizing friction and allowing compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing mechanical inertial igniters are used for low-g and long-duration firing accelerations, then the device can detect acceleration events, but the device size becomes too large and reliability decreases
Solution Approach 1:
The striker mass is positioned within a hollow cylindrical delay mechanism, with the spring element contained within the delay mechanism structure. This nested arrangement allows compact packaging of multiple functional components (striker, spring, delay mechanism) in a small volume, enabling reliable low-g detection without increasing overall igniter size
Solution Approach 2:
The igniter is divided into functionally independent segments: the striker mass for impact generation, the spring element for energy storage, and the hollow cylindrical delay mechanism for timing and filtering. This segmentation allows each component to be optimized for its specific function while contributing to overall compactness and reliability
2Reliability
If the striker mass is released upon detection of all-fire conditions, then reliable ignition is achieved, but accidental activation from shocks may occur
Solution Approach 1:
The spring element is pre-compressed and stored within the hollow cylindrical delay mechanism before the firing event. This preliminary energy storage ensures that when the striker mass is released, it immediately receives the force needed for reliable ignition, while the delay mechanism ensures release only occurs after the prescribed acceleration duration has been met
Solution Approach 2:
The hollow cylindrical delay mechanism acts as an intermediary between the acceleration detection and striker release. It filters out short-duration shock events by requiring a minimum acceleration duration threshold, allowing only legitimate all-fire conditions to trigger striker release while blocking accidental activation from brief shocks
3Volume of moving object
If the device is made compact for miniaturization, then volume is reduced, but friction increases and reliability decreases
Solution Approach 1:
The striker mass is designed to rotate about a vertical axis within the hollow cylindrical delay mechanism, allowing it to maintain a consistent radial position regardless of the device's orientation during low-g acceleration. This rotational freedom ensures the striker can reliably reach the percussion primer from any angular position, maintaining operational reliability in a compact configuration
Solution Approach 2:
The design changes the motion parameter of the striker mass from linear translation to rotational movement about a vertical axis. This parameter change allows the striker to navigate compact spaces more effectively, reducing friction with surrounding structures while maintaining the ability to deliver reliable impact to the percussion primer
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 ignition with high safety and compactness, differentiating no-fire from all-fire conditions, and maintaining functionality despite accidental shocks, suitable for munitions with low-g and long-duration accelerations.
Implementation Method 1
potential energy stored in a spring element
Implementation Method 2
striker mass mechanism with potential energy stored in a spring element, released upon detection of prescribed all-fire conditions
Data Source
AI summary
An inertial mechanism including a member rotatable about an axis between activatable and activated positions, in the activatable position a first center of mass of the member is offset from the axis in a direction perpendicular to a direction of acceleration, the member having a surface; and another member rotatable about an axis between rest and activated positions, the rest position being where the second member cannot be moved into its activated position from an acceleration event, the other member also having a surface, the surfaces engage with each other when the member moves to its activated position to move the other member from its rest position to its activatable position, which is also where a center of mass of the other member is offset from its axis in the direction perpendicular to the direction of the acceleration.