Ceramic Shield for Induction Ignition Device
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Solution Overview
Problem
Existing magnetic induction firing devices for ammunition are prone to deterioration after a few shots, leading to safety and toxicity concerns due to the use of fibrous materials and resins, which are not suitable for repeated use in confined environments.
Innovation Solution
A ceramic shield made from materials like zirconia, alumina, silicon carbide, or silicon nitride with specific mechanical and surface properties, such as high breaking stress, low porosity, and controlled roughness, is used to protect the induction device, allowing it to withstand multiple shots without significant alteration and ensuring operator safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fibrous material shield (asbestos or fiberglass with phenolic resin) is used to protect the induction device, then the device can withstand thermomechanical stresses and be reused for several firings, but the material exhibits high toxicity making it hazardous to operator health
Solution Approach 1:
The patent changes the material parameters of the shield from fibrous materials (asbestos, fiberglass with phenolic resin) to monolithic ceramic materials (alumina, zirconia, silicon carbide, silicon nitride). This material substitution eliminates toxicity while maintaining or improving mechanical strength, thermal resistance, and reusability properties.
Solution Approach 2:
The patent employs advanced ceramic materials that combine multiple desirable properties: high flexural strength (≥50 MPa), high toughness (≥2 MPa·m−1/2), low porosity (<15%), and resistance to thermomechanical stress. These ceramic materials provide both the structural integrity needed for reusability and the non-toxicity required for operator safety.
2Strength
If the shield material has high flexural strength and toughness to withstand firing stresses, then the device can be reused without alteration, but the material must also have low porosity and controlled grain size to prevent cracking and maintain integrity
Solution Approach 1:
The patent specifies precise material parameters: flexural strength ≥50 MPa, toughness ≥2 MPa·m−1/2, porosity <15%, grain size ≤300 micrometers. These controlled parameters ensure the shield can withstand firing stresses while preventing crack propagation and maintaining structural integrity for repeated use.
Solution Approach 2:
The patent applies different surface treatments to different regions of the shield. The surface in contact with the chamber has specific roughness control (Ra < 5 micrometers) to prevent crack initiation, while the bulk material provides overall strength and toughness. This localized quality control enhances overall reliability.
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 ceramic shield effectively withstands high pressures and temperatures during firing, maintaining structural integrity and safety, enabling repeated use without health risks to operators, even in challenging environments.
Implementation Method 1
The shield material exhibits a flexural strength at 20°C, as measured according to standard NF-EN 843-1 (April 1995), exceeding 50 MPa
Implementation Method 2
ignition by magnetic or electromagnetic induction and combustion of a propellant charge
Implementation Method 3
the induced current heats the charge by Joule heating, causing it to explode
Data Source
Figure 1
AI summary
A device (2) for igniting a munition consisting of a projectile (4) and its propelling charge (5), comprising a breech (13) that is suitable for coming into contact with a chamber (6) of a barrel (1) loaded with said munition, said breech (13) closing said barrel (1) in the firing position, in which said breech (13) comprises a magnetic (7) or electromagnetic induction priming device allowing the combustion of the propelling charge (5) to be triggered and the projectile (4) to be fired from said barrel (1), a shield (3) positioned between the induction priming device (7) and the chamber (6) of said barrel, comprising a ceramic material made of an oxide, of a carbide, of a nitride, of an oxynitride or of a boride of at least one element chosen from silicon, aluminum, zirconium, boron, titanium, tungsten and hafnium, said ceramic material comprising grains, the maximum diameter of which is smaller than or equal to 500 micrometers, the shield being a right cylinder having a circular base.