Inertial Igniter Inclined Surface Acceleration Discrimination
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Solution Overview
Problem
Inertial igniters for thermal batteries in munitions applications face challenges in distinguishing between firing acceleration and accidental events, leading to safety concerns of accidental ignition, especially at low impact levels.
Innovation Solution
An inertial igniter design featuring a mass element and spring element with an inclined surface, where the mass element moves to ignite pyrotechnic materials only upon firing setback acceleration, incorporating a delay mechanism to ensure ignition during set-forward acceleration, and can be adapted for electrical switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If inertial igniters are designed to operate at relatively low impact levels, then the device can be activated by lower acceleration forces, but the safety risk of accidental ignition increases due to difficulty in distinguishing firing acceleration from accidental events
Solution Approach 1:
The patent employs a dual-stage dynamic response mechanism where the igniter system exhibits different behavioral characteristics under different acceleration profiles. The first stage uses a low-threshold inertial igniter that responds to initial setback acceleration, while the second stage uses a delay mechanism that only completes ignition under sustained or reversed acceleration patterns characteristic of firing events, not accidental impacts.
Solution Approach 2:
The delay mechanism is pre-configured to require a specific sequence of acceleration events before ignition can occur. The system performs preliminary discrimination by requiring both initial movement and subsequent delay period completion, which anticipates the firing acceleration profile while preventing activation by single-impact accidental events.
2Reliability
If a delay mechanism is incorporated to ensure ignition during set-forward acceleration, then the reliability of controlled ignition is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple functions into integrated components. The delay mechanism is merged with the inertial igniter assembly such that the same structural elements serve both the delay function and the ignition function. The mass element, spring element, and inclined surface work together to provide both the delay mechanism operation and the final ignition strike, reducing overall system complexity.
Solution Approach 2:
The inertial igniter components serve multiple purposes: the mass element provides both inertia-based delay timing and the striking mass for ignition; the spring element provides both the restoring force for the delay mechanism and the propelling force for the ignition strike; the inclined surface provides both the delay pathway and the ignition trajectory. This multi-functionality reduces the need for separate dedicated components.
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 design ensures safe and controlled ignition of thermal batteries by differentiating between firing and accidental accelerations, preventing accidental ignition and ensuring reliable operation in high-G munitions applications.
Implementation Method 1
The inertial igniters operate based on the firing acceleration
Implementation Method 2
a spring element attached at one end to the body and at another end, at least indirectly, to the mass element
Implementation Method 3
a blend of Fe and KClO4. Thermal batteries utilize a molten salt to serve as the electrolyte upon activation
Data Source
AI summary
An electrical switch including: a body; a mass element; a spring element attached at one end to the body and at another end, at least indirectly, to the mass element; and an inclined surface upon which the mass element moves from a resting position to an all-fire position. The inclined surface being inclined with respect to a firing setback acceleration. When the body experiences the firing setback acceleration, the mass element travels at least across the inclined surface against a force of the spring element to contact an electrical contact and close a circuit.