Polymeric Ammunition Casing Geometry for Weight Reduction
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Solution Overview
Problem
Conventional ammunition cartridge casings made of metals like brass and aluminum are heavy and prone to corrosion, with polymeric materials failing to meet mechanical and thermal demands, especially during firing, due to inadequate design geometries and material properties.
Innovation Solution
A novel ammunition cartridge casing geometry featuring a polymeric caselet with a specific wall thickness ratio greater than 1, optimized for polymeric materials, which includes a cap and caselet interconnected via snap fit or threads, using materials like polyphenylsulfone or polycarbonate, and a metallic cap to enhance mechanical strength and resistance to corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If polymeric materials are used for cartridge casing fabrication, then weight is reduced and corrosion resistance is improved, but mechanical strength and thermal stability are insufficient
Solution Approach 1:
The patent employs composite construction by combining polymeric materials with metallic components (brass or steel cap, aluminum or polymer base). This hybrid approach allows the polymeric case body to provide weight reduction and corrosion resistance, while the metallic cap and optimized geometry compensate for mechanical strength deficiencies, achieving overall structural integrity suitable for high-pressure firing conditions.
Solution Approach 2:
The patent modifies geometric parameters of the polymeric case, specifically optimizing wall thickness distribution along the case length. The case features variable wall thickness with thicker sections at the base and shoulder areas where stress concentration occurs, and thinner sections toward the mouth. This parameter optimization enables the polymeric material to withstand firing pressures while maintaining weight advantages.
2Ease of manufacture
If conventional cartridge casing geometry is used with polymeric materials, then manufacturing simplicity is maintained, but mechanical performance under firing stress is inadequate
Solution Approach 1:
The patent applies local quality optimization by varying the wall thickness of the polymeric case along its length rather than using uniform thickness. The case has thicker walls at the base and shoulder regions where firing stresses are concentrated, and thinner walls toward the mouth where stresses are lower. This localized geometric modification enhances structural reliability at critical stress points while maintaining overall manufacturing simplicity through injection molding processes.
3Ease of manufacture
If uniform wall thickness is used in polymeric case, then manufacturing is simplified, but stress distribution during firing is inadequate
Solution Approach 1:
The patent implements parameter changes by transitioning from uniform wall thickness to variable wall thickness distribution. The polymeric case is designed with thicker sections at the base and shoulder where peak stresses occur during firing, and progressively thinner sections toward the mouth. This geometric parameter optimization enables better stress distribution and load bearing capacity while remaining compatible with injection molding manufacturing processes.
Data Source
AI summary
An ammunition cartridge casing having a geometry designed to allow for the use of polymeric materials in forming the walls of the cartridge casing of an ammunition article, and methods of reusing such cartridges are provided. More specifically, the ammunition cartridge has a specified ratio between the wall-thicknesses of select portions of an ammunition article's cartridge casing such that polymeric materials may be used in the construction of the ammunition article cartridge casings.