Hybrid Annular-Cantilevered Snap-Fit Joint for Artillery

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current methods for assembling spin-stabilized artillery projectiles, such as threaded joints with adhesives and friction-based surfaces, are prone to failure under high torque loads, leading to component separation and manufacturing inconsistencies.

Innovation Solution

A hybrid annular-cantilevered snap fit joint using a spider assembly with pins and leaf springs, where the spider assembly is positioned between the fore and aft portions of the projectile, providing a secure and consistent connection through a tooth and groove arrangement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If threaded joints with adhesive are used to assemble projectile components, then the joint strength is improved, but the manufacturing complexity and reliability under high torque loads deteriorate

Engineering Contradiction:

Improvejoint strengthVSAvoidmanufacturing complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent replaces the threaded mechanical joint with a snap-fit mechanical joint that uses elastic deformation of cantilevered fingers to create locking engagement. This eliminates the need for threads and adhesive while maintaining joint strength through purely mechanical elastic locking, thereby reducing manufacturing complexity and improving reliability under torque loads.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The snap-fit joint uses dynamic elastic deformation of the cantilevered fingers during assembly and operation. The fingers flex during engagement and maintain continuous elastic stress to provide locking force, allowing the joint to dynamically adapt to loads rather than relying on static threaded engagement and adhesive bonding.

Inventive Principle:

Principle #15Dynamics

2Ease of manufacture

If friction-based surfaces such as face knurling are used, then the ease of manufacture is improved, but the measurement precision and reliability under dynamic conditions deteriorate

Engineering Contradiction:

Improveease of manufactureVSAvoidfriction measurement precision

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent replaces friction-based mechanical engagement with elastic mechanical locking using cantilevered snap-fit fingers. Instead of relying on friction between knurled surfaces, the joint uses the elastic recovery force of bent fingers to create positive mechanical locking, eliminating the need to measure or control friction coefficients in dynamic environments.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If threaded joints with locking adhesive are used, then the joint strength is improved, but the reliability under high torque and tensile loads deteriorates

Engineering Contradiction:

Improvejoint strengthVSAvoidreliability under torque and tensile loads

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent replaces the threaded joint with adhesive system with a purely mechanical snap-fit joint using cantilevered fingers. The elastic fingers provide continuous locking force through their bent geometry, creating reliable mechanical engagement that resists both torque and tensile loads without relying on adhesive bonding, thereby improving reliability in high-stress dynamic conditions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The snap-fit joint utilizes dynamic elastic deformation of the cantilevered fingers to maintain continuous locking force. The fingers flex during engagement and operation, providing adaptive mechanical locking that reliably resists varying torque and tensile loads without the failure modes associated with adhesive or threaded joints.

Inventive Principle:

Principle #15Dynamics

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 ensures robust and reliable assembly of projectile components, capable of withstanding high accelerations and torque loads, while simplifying the manufacturing process and eliminating the need for precise friction measurement.

Implementation Method 1

a plurality of leaf springs arranged circumferentially around an opening of the aft portion and extending in an axial direction

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

The components are then held together by forcibly joining them using a hybrid annular and cantilevered snap fit joint. A tooth and groove arrangement exists where the teeth are at the end of a spring-leaf like feature

Methodology Applied

Scientific EffectMechanical interlocking: Mechanical Fastener

Data Source

PatentUS11624597B1Hybrid annular-cantilevered snap-fit joint

Publication Date: 2023.04.11 UNITED STATES OF AMERICA THE AS REPRESENTED BY THE SEC OF THE ARMY

AI summary

A safe and reliable multi-component projectile enables cost effective manufacturing and assembly of the projectile. Major components of the projectile are joined by a plurality of shear pins interfacing with scalloped geometry of the components. The components are then held together by forcibly joining them using a hybrid annular-cantilevered snap fit joint. The tooth and groove arrangement exists where the teeth are at the end of a spring-leaf like feature of one of the mating parts and the groove is located on the opposite mating part.