Axially Compact Inertial Igniter for Thermal Batteries
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Solution Overview
Problem
Current inertial igniters for thermal batteries are too large and unsuitable for small, low-power applications, requiring external power sources and being prone to accidental ignition, with a need for a compact, safe, and reliable ignition mechanism that can withstand high accelerations and long storage periods.
Innovation Solution
A novel miniature inertial igniter design with a slidable striker and pyrotechnic material system, using a percussion cap primer and biasing mechanisms to ensure ignition only at specified acceleration levels, allowing direct initiation of pyrotechnics within the thermal battery without intermediate materials and housed within the battery for reduced volume and enhanced safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing inertial igniters are used in thermal batteries, then reliable ignition at high accelerations is achieved, but the igniter size becomes too large for small and miniaturized thermal batteries
Solution Approach 1:
The striker assembly is nested within the housing, with the striker positioned axially within the cylindrical cavity. The biasing mechanism and locking balls are integrated within the same housing structure, creating a compact nested arrangement that reduces overall igniter volume while maintaining functional separation of components.
Solution Approach 2:
The invention transitions from a larger, more distributed igniter configuration to a compact axial arrangement where all critical components (striker, pyrotechnic material, biasing mechanism) are positioned along the axial dimension within a single housing, enabling miniaturization while preserving ignition reliability.
2Reliability
If electrical igniters are used to provide controlled pyrotechnic reaction, then reliable ignition is achieved, but onboard batteries or power sources are required which increase complexity and volume
Solution Approach 1:
The invention replaces electrical ignition systems with a purely mechanical inertial ignition system. The striker is accelerated by inertial forces during high-G events and mechanically impacts the pyrotechnic material to initiate combustion, eliminating the need for electrical power sources, batteries, or associated control systems.
Solution Approach 2:
The igniter uses the thermal battery's own operational environment (high acceleration during munitions flight) to trigger ignition. The inertial forces generated during normal munitions operation automatically activate the striker mechanism, making the system self-activating without external power sources or control systems.
3Object-affected harmful factors
If inertial igniters are designed to operate at relatively low impact levels, then safety against accidental ignition is improved, but the igniter size increases to accommodate safety mechanisms
Solution Approach 1:
The invention sets a specific acceleration threshold parameter (high-G event) that must be exceeded to trigger ignition. The biasing mechanism and locking balls are calibrated to maintain the striker in a blocked position during normal low-acceleration handling, and only release during high-G munitions operation, providing inherent safety without requiring additional safety mechanisms.
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 significantly shorter, safer, and more reliable inertial igniter that can initiate thermal batteries at high accelerations while preventing accidental ignition, with improved storage and shelf life, and reduced manufacturing costs, suitable for small thermal batteries in munitions.
Implementation Method 1
a first biasing means for biasing the striker... a second biasing means for biasing the pyrotechnic material in the direction opposite the acceleration
Implementation Method 2
when the acceleration time profile is greater than the predetermined threshold the one or more locking balls are released... to permit relative movement of the striker with the first member... such that the striker strikes the pyrotechnic material
Data Source
AI summary
An inertial igniter including: a first member having a wall and internal cavity; a second member slidable in the internal cavity, a striker disposed thereon and a first concave portion; a third member slidable on an exterior surface of the wall, a second concave portion; biasing springs for biasing the first and second members in a direction opposite an acceleration; locking balls in the first and second concave portions for preventing movement of the second and third members when the acceleration time profile is below a predetermined threshold; and a percussion cap primer on the first member; wherein when the acceleration time profile is greater than the predetermined threshold the locking balls are released from the concave portions to first permit relative movement of the third member with the first member and after a time delay to permit relative movement of the second member with the first member.