Mechanical Inertial Igniter Locking for High-Drop Safety

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Solution Overview

Problem

Current inertial igniters for thermal batteries fail to ensure safe non-initiation during drops from high heights, such as up to 40 feet, which result in high impact deceleration levels, while also requiring reliable ignition during firing accelerations, posing challenges for compact and low-volume designs suitable for munitions applications.

Innovation Solution

The development of a mechanical inertial igniter with a deployable locking mechanism that prevents striker mass release during high-height drops, utilizing a combination of spring-loaded and sliding elements to differentiate between accidental drops and firing accelerations, ensuring safe non-initiation and reliable ignition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the inertial igniter is designed to initiate at lower acceleration levels, then the firing reliability is improved, but the safety against accidental drops deteriorates

Engineering Contradiction:

Improvefiring reliabilityVSAvoidaccidental initiation risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent employs dynamic elements including a striker mass that can move between locked and unlocked positions, and a locking ball that dynamically responds to acceleration forces. The system transitions from a static design to one where components move and change state based on the magnitude and duration of applied acceleration, enabling differentiation between firing and drop events

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The locking ball is pre-positioned to engage with the striker mass before firing occurs. During normal handling and accidental drops, the locking ball remains in place to prevent initiation. Only when the predetermined acceleration threshold is exceeded does the locking ball move to allow striker release, ensuring safety against premature initiation while maintaining firing reliability

Inventive Principle:

Principle #10Preliminary action

2Volume of moving object

If the inertial igniter structure is made compact, then the volume is reduced, but the ability to withstand high impact shocks deteriorates

Engineering Contradiction:

Improveigniter volumeVSAvoidhigh-height drop safety

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent introduces a temporal dimension to the safety mechanism by considering not just the magnitude but also the duration of acceleration events. The locking mechanism is designed to withstand short-duration high-impact shocks from drops while responding to longer-duration firing accelerations, effectively adding time as a differentiating dimension to the compact design

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The system changes the threshold parameters for initiation by designing the locking ball and striker mass interaction to require a specific acceleration magnitude and duration combination. This allows the compact igniter to differentiate between harmful drop impacts and beneficial firing accelerations, maintaining high-height drop safety within a reduced volume

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the striker mass is held securely to prevent accidental release, then the safety is improved, but the ease of release during firing deteriorates

Engineering Contradiction:

Improvesafety against accidental ignitionVSAvoidstriker release reliability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The locking ball serves as an intermediary element between the striker mass and the acceleration forces. It provides a mechanical interface that securely holds the striker during normal operations and accidentally, yet allows controlled release when the locking ball itself is subjected to sufficient acceleration force during firing

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system uses the firing acceleration itself to overcome the locking mechanism. The same force that needs to be withstood during drops (when duration is short) becomes the activating force during firing (when duration is sufficient), allowing the striker to self-release without external intervention while maintaining safety against accidental drops

Inventive Principle:

Principle #25Self-service

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 effectively prevents initiation during high-height drops with deceleration levels up to 18,000 Gs while allowing reliable ignition during firing accelerations, enhancing safety and reliability for thermal batteries in munitions, and is designed to be compact and scalable for various thermal battery sizes.

Implementation Method 1

spring-loaded elements to differentiate between accidental drops and firing accelerations

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

mechanical inertial igniter with high-height drop safety feature

Methodology Applied

Scientific EffectInertia: Inertia

Data Source

PatentUS9123487B2Mechanical inertial igniter with high-height drop safety feature for thermal batteries and the like

Publication Date: 2015.09.01 OMNITEK PARTNERS LLC

AI summary

A method for initiating a thermal battery including: releasing an engagement between an element and a striker mass upon an acceleration time and magnitude greater than a first threshold; and moving at least one member into a path of the element to prevent the element from releasing the striker mass only where the acceleration time and magnitude is greater than a second threshold, the second threshold being greater than the first threshold.