Two-Stage Cartridge Case Neck for Retention Without Crimping
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Solution Overview
Problem
Existing ammunition cartridge designs face challenges in balancing retention force, shelf-life, durability, and ballistic performance, particularly in high-strength materials like steel, which often require crimping and can lead to surface damage and corrosion.
Innovation Solution
A two-stage neck design for the cartridge case featuring an interference band and a clearance band, providing varying retention forces through interference and clearance fits, reducing the need for crimping and enhancing surface integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength materials like steel are used for cartridge cases, then strength and durability are improved, but surface damage and corrosion occur due to crimping
Solution Approach 1:
The neck is segmented into two distinct zones: an interference zone with a smaller internal diameter that provides strong retention through interference fit, and a clearance zone with a larger internal diameter that eliminates crimping operations. This segmentation allows the use of high-strength materials like steel without the surface damage caused by traditional crimping processes.
Solution Approach 2:
Different regions of the neck are given different dimensional properties to serve different functions. The interference zone has a tighter tolerance and smaller diameter for strong projectile retention, while the clearance zone has a larger diameter and tighter tolerance to prevent contact with the projectile ogive, thereby preventing surface damage and corrosion in high-strength materials.
2Ease of manufacture
If traditional single-stage neck design is used, then manufacturing is simpler, but retention force and ballistic performance are insufficient
Solution Approach 1:
The neck is divided into two functional zones with different diameters: the interference zone provides strong retention force through interference fit, while the clearance zone prevents projectile contact. This segmentation achieves superior retention force and ballistic performance compared to traditional single-stage designs.
Solution Approach 2:
The internal diameter parameter of the neck is varied along its length, creating two distinct zones with different dimensional characteristics. The interference zone has a smaller diameter for strong retention, while the clearance zone has a larger diameter to prevent contact, thereby improving both retention force and ballistic performance.
3Force
If interference fit is increased to improve retention force, then retention force is improved, but crimping requirements increase causing surface damage
Solution Approach 1:
The neck is segmented into an interference zone that provides strong retention force through interference fit, and a clearance zone that eliminates the need for crimping operations. The interference zone achieves the required retention force without subjecting the high-strength material to crimping-induced surface damage.
Solution Approach 2:
The interference zone is localized to a specific portion of the neck where strong retention is needed, while the clearance zone provides a non-contact region that prevents surface damage. This local differentiation allows high retention force without the harmful effects of crimping on the overall projectile surface.
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 two-stage neck design achieves comparable retention forces to brass while minimizing crimping needs, improving durability and reducing corrosion, suitable for high-strength materials like steel, and maintaining ballistic performance.
Implementation Method 1
The interior of the two-stage neck comprises an interference band that is adjacent the second end of the body and comprises an interference diameter extending an interference length along the two-stage neck, the interference band configured to provide an interference fit with the projectile resulting in an interference retention force
Implementation Method 2
The interior of the two-stage neck also comprising a clearance band comprising a clearance diameter and extending a clearance length along the two-stage neck, the clearance diameter being greater than the interference diameter, the clearance band configured to provide an interference fit with the projectile resulting in a clearance retention force
Data Source
AI summary
Devices and methods for reducing tension force on a projectile by a neck of a cartridge case. A two-stage neck has a clearance band and an interference band, the clearance band providing a reduced retention force on the projectile relative to the interference band.