Vibration Resistant Exploding Foil Initiator Assembly
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Solution Overview
Problem
Vibration in initiator assemblies can cause the output charge to break apart and migrate, preventing the exploding foil initiator from detonating the input charge due to additional mass on the flyer or tilting it, leading to insufficient acceleration and improper shock distribution.
Innovation Solution
The design includes a housing with specific cavity portions and a holder structure that secures the input charge and output charge, with an exploding foil initiator mounted to a base, ensuring the flyer strikes the input charge perpendicular and maintaining a compressive load on the output charge to prevent movement and ensure detonation, even under vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output charge is not secured in the cavity, then the assembly is simpler to manufacture, but the output charge will migrate under vibration causing failure of the initiator
Solution Approach 1:
The cavity is divided into three distinct portions: a first cavity portion for the base/EFI assembly, a second cavity portion for the input charge assembly, and a third cavity portion for the output charge. This segmentation allows each component to be securely positioned in its designated space, preventing migration under vibration while maintaining a manageable overall structure.
Solution Approach 2:
A partition wall is introduced as an intermediary structure between the first and second cavity portions. This partition wall includes a through-bore that allows the base/EFI assembly to pass through while maintaining separation between different functional zones, preventing output charge migration into the input charge area.
2Speed
If the flyer is accelerated over a short distance, then the initiator is more compact, but the flyer may not achieve sufficient velocity to detonate the input charge
Solution Approach 1:
The barrel is designed with varying cross-sectional areas along its length, creating different pressure zones that optimize flyer acceleration. The first barrel portion has a different cross-sectional area than the second barrel portion, allowing the flyer to achieve sufficient velocity over the available distance while maintaining compact overall dimensions.
3Reliability
If the flyer strikes the input charge perpendicular to the barrel axis, then the shock is more effective, but any tilt causes the shock to be distributed over time reducing detonation initiation
Solution Approach 1:
The holder is pre-formed with a specific geometry that includes a tilt angle, and the input charge is positioned in the holder at a predetermined orientation. This preliminary configuration ensures that when the flyer strikes the input charge, the shock is delivered perpendicular to the barrel axis, maximizing detonation initiation reliability without requiring complex active alignment mechanisms.
4Stability of the object's composition
If additional mass is added to the output charge to ensure it stays in place, then the charge is more secure, but the flyer acceleration is reduced preventing detonation
Solution Approach 1:
The cavity is segmented into separate portions for the output charge and the base/EFI assembly, with the output charge confined to the third cavity portion. This spatial separation allows the output charge to be secured in place without adding mass that would hinder flyer acceleration, as the securing mechanism is geometric confinement rather than mass addition.
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 the output charge from migrating and ensures the flyer achieves the necessary velocity and orientation to detonate the input charge reliably, maintaining the assembly's functionality under vibrational stress.
Implementation Method 1
Electrical energy input to an exploding foil initiator causes a thin metal bridge to vaporize, which propels a flyer through a barrel
Implementation Method 2
The flyer must be accelerated over a relatively short distance (i.e., less than 0.050 inch) to a velocity that is sufficient to initiate the detonation of the input charge
Implementation Method 3
the shock produced by contact between the flyer and the input charge is distributed over time (rather than all at once) so that the input charge is not shocked to a degree that initiates detonation of the input charge
Implementation Method 4
Initiator assemblies are employed to detonate an input charge to release energy that is subsequently employed to initiate detonation, deflagration or combustion in an output charge
Data Source
AI summary
An initiator assembly that includes a housing, a base, an exploding foil initiator, an input charge assembly and an output charge. The housing and the base cooperate to define a cavity. The exploding foil initiator and the output charge are received into the cavity. The input charge assembly is received in the cavity between the exploding foil initiator and the output charge. The input charge assembly includes a holder, which has first and second axial ends, and an input charge. A charge aperture is formed through the first axial end of the holder and does not extend through the second axial end of the holder. The input charge is formed of an explosive material and is received into the charge aperture.