Countermass Container with Differential Envelope Sections

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Solution Overview

Problem

Recoilless weapons employing the countermass principle often experience symmetry problems leading to oblique ejection of the countermass, asymmetrical gas leakage, and pressure differences, resulting in reduced repeatability and hit rate compared to conventional gas nozzle systems.

Innovation Solution

A countermass container with an envelope divided into a stronger front section and a weaker rear section, featuring splines for duct creation between the sections, and made of materials like rigid plastic and closed-cell polyethylene foam, along with a formable countermass such as steel grit or liquid, to enhance balance and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a countermass container with uniform envelope construction is used, then the structure is simple and easy to manufacture, but symmetry problems occur leading to oblique ejection and reduced hit rate

Engineering Contradiction:
Improveenvelope construction simplicityVSAvoidejection symmetry and hit rate
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The envelope is constructed with different wall thicknesses in different sections: the front section has a first wall thickness while the rear section has a second wall thickness that is less than the first. This local differentiation creates controlled asymmetry that compensates for pressure distribution variations during ejection, improving symmetry and hit rate without significantly complicating manufacturing.

Inventive Principle:
Principle #3Local quality

2Strength

If the envelope is made uniformly strong throughout, then structural integrity is maintained, but symmetry problems and gas leakage occur reducing repeatability

Engineering Contradiction:
Improveenvelope structural integrityVSAvoidrepeatability and symmetry
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The envelope employs localized strength variation where the front section maintains greater wall thickness for structural integrity during initial pressurization, while the rear section has reduced wall thickness to facilitate controlled ejection. This local differentiation ensures the envelope remains strong where needed while achieving symmetric ejection behavior for improved repeatability.

Inventive Principle:
Principle #3Local quality

3Device complexity

If a conventional countermass container design is used, then the weapon system is simple, but sideway disturbances and pressure differences reduce hit rate

Engineering Contradiction:
Improvecontainer design complexityVSAvoidhit rate and pressure balance
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The countermass container implements differential wall thickness where the front section has a first wall thickness and the rear section has a second wall thickness less than the first. This simple structural modification balances pressure distribution during ejection, reducing sideway disturbances and improving hit rate without significantly increasing device complexity.

Inventive Principle:
Principle #3Local quality

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

This design achieves acceptable recoil levels, increased repeatability, reduced sideway disturbances, and improved hit rates by ensuring balanced ejection and reduced pressure differences during firing.

Implementation Method 1

gun powder exploding between the ammunition unit and the countermass

Methodology Applied
Scientific EffectGun powder explosion: Combustion

Implementation Method 2

the rear section of the envelope having a weaker construction than the front section of the envelope to more easily crack than the front section of the envelope

Methodology Applied
Scientific EffectFracture mechanics: Fracture Mechanics

Data Source

PatentEP2815199B1A countermass container for use in a recoilless weapon and a recoilless weapon comprising such a countermass container
Publication Date: 2020.04.29 SAAB AB
  • EP2815199B1 patent drawingFigure 1
  • EP2815199B1 patent drawingFigure 2~3
  • EP2815199B1 patent drawingFigure 4a~6b

AI summary

The present invention relates to a countermass container (13) for use in a recoilless weapon (1) comprising an envelope (16) enclosing a countermass (4). The invention also refers to a recoilless weapon (1) comprising a barrel (2) accommodating an ammunition unit (3) such as a projectile or shell, a propellant charge (12) and a countermass container (13) comprising an envelope (16) enclosing a countermass (4), the barrel (2) comprising a front end opening for firing the ammunition unit (3) out of the barrel (2) and a rear end opening (15) for ejecting the comprised envelope (16) and countermass (4) of the counter mass container (13). The invention proposes a solution to symmetry problems and increases the hit rate. According to the proposed solution the envelope (16) is divided into a front section (17) and a rear section (18), the rear section ( 18) of the envelope ( 16) having a weaker construction than the front section (17) of the envelope (16) to more easily crack than the front section (17) of the envelope.