Programmable Inertial Igniter with Acceleration-Responsive Stops
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Solution Overview
Problem
Existing inertial igniters for thermal batteries in gun-fired munitions are large and unsuitable for small, low-power applications, requiring external power sources and lacking the ability to differentiate between accidental and initiation accelerations, posing safety concerns and manufacturing challenges.
Innovation Solution
A programmable inertial igniter design featuring a striker mass, biasing element, and movable members with stops that are configured to prevent accidental ignition by moving into a second position only under predetermined acceleration profiles, eliminating the need for external power sources and allowing for varied all-fire acceleration requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If existing inertial igniters are used for thermal batteries, then reliable ignition can be achieved, but the igniters are large and not suitable for small and miniaturized applications
Solution Approach 1:
The igniter is divided into separate functional modules: a striker assembly, a safety mechanism with movable members and stops, and a pyrotechnic element. This segmentation allows each component to be optimized for miniaturization while maintaining overall reliability, as each module can be independently designed and assembled at reduced scale.
Solution Approach 2:
The striker assembly is positioned within a housing that contains the safety mechanism components. The movable members with stops are integrated into the housing structure, creating a nested arrangement that maximizes space efficiency and reduces the overall volume of the igniter while maintaining all necessary functions.
2Device complexity
If existing inertial igniters are used, then ignition can be initiated, but external power sources and related complexity are required
Solution Approach 1:
The igniter uses the kinetic energy from the accelerating force itself to drive the striker against the pyrotechnic element. The safety mechanism automatically engages and disengages based on the acceleration profile, requiring no external power source, control systems, or additional energy storage components.
Solution Approach 2:
The patent replaces electrical or chemical power sources with a purely mechanical inertial mechanism. The striker is propelled by the acceleration force acting on a mass, and the safety stops are actuated by the same mechanical motion, eliminating the need for batteries, motors, or electronic control circuits.
3Reliability
If existing inertial igniters are used, then ignition can occur, but safety concerns arise from inability to differentiate accidental drops from firing acceleration
Solution Approach 1:
The safety mechanism uses movable members that can dynamically change position based on the acceleration profile. The stops are positioned to block the striker under normal conditions but move out of the way when a specific acceleration threshold is reached, allowing the system to adapt its safety state based on the dynamic characteristics of the applied force.
Solution Approach 2:
The mechanism differentiates between accidental and intentional acceleration by monitoring the magnitude and duration of the applied force. The safety stops are designed to remain engaged during low-acceleration events (accidental drops) but disengage during high-acceleration events (firing), using parameter thresholds to control the safety state.
4Ease of manufacture
If existing inertial igniters are used, then ignition can be achieved, but manufacturing complexity and cost increase due to labor intensive processes
Solution Approach 1:
Multiple safety functions are combined into a single integrated mechanism. The movable members with stops serve both as safety blocks and as acceleration sensors, while the striker assembly integrates both the ignition element and the safety interaction point. This merging reduces the number of separate components and simplifies assembly procedures.
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 compact, low-cost inertial igniter that safely initiates only under high acceleration profiles, ensuring reliable ignition during firing while preventing accidental ignition, and can be scaled for various thermal battery sizes, enhancing safety and manufacturing efficiency.
Implementation Method 1
a biasing element for biasing the striker mass towards a percussion primer
Implementation Method 2
a striker mass movable relative to the housing... allowing the portion of the striker mass to strike the percussion primer
Data Source
AI summary
An inertial igniter including: a housing; a striker mass movable relative to the housing; a biasing element for biasing the striker mass towards a percussion primer; one or more movable members each having one or more stops, the one or more stops having a first position for preventing a portion of the striker mass from striking the percussion primer and a second position allowing the portion of the striker mass to strike the percussion primer; wherein the movable members move the one or more stops to the second position when subjected to a predetermined acceleration profile.