Sacrificial Hose Fitting Assembly Strain Relief
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Solution Overview
Problem
Current hose fitting assemblies for high-pressure flexible hoses, particularly in applications like aircraft fuel lines and brake lines, face challenges in withstanding dynamic flexing and fatigue while minimizing weight and cost, as existing stress relief devices often require specialized construction and additional components, and fail to provide adequate strain relief and abrasion resistance.
Innovation Solution
A hose fitting assembly that forms a sacrificial end fitting with a clamping sleeve and swaging collar, using less than full tensile strength stainless steel braiding, which engages a flexible high-pressure hose with external and internal threads to provide a burst strength of at least 5,000 psi and tensile strength of 325 lbs, while requiring less than 15 ft-lbs torque for assembly, and includes a circumferentially compressible section for strain relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional stress relief devices are added to hoses, then protection against fatigue and bending is improved, but weight increases significantly (5-10 pounds of supporting structure per pound of stress relief)
Solution Approach 1:
The patent combines the stress relief function directly into the hose fitting assembly itself, merging what were previously separate components (stress relief device + fitting) into a single integrated unit. The fitting includes a barbed insertion stem that engages the hose and a clamping mechanism that provides stress relief without requiring additional separate components, thereby achieving fatigue protection without the weight penalty of separate stress relief devices and their supporting structures.
Solution Approach 2:
The hose fitting assembly performs multiple functions simultaneously: it provides the mechanical connection (fitting), stress relief during flexing, strain relief during pulling, and abrasion resistance. The barbed insertion stem and clamping mechanism are designed to handle multiple stress types (bending, pulling, abrasion) within a single component, eliminating the need for multiple specialized components and their associated supporting structures.
2Reliability
If sophisticated stress relief devices are used, then protection against dynamic flexing and fatigue is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The fitting is segmented into distinct functional zones: the barbed insertion stem for hose engagement, the threaded portion for connection, and the clamping mechanism for stress relief. This segmentation allows each part to be optimized for its specific function while maintaining overall simplicity. The barbs provide mechanical interlocking, the threads provide adjustable connection, and the clamping mechanism provides stress relief, with each segment performing its function independently.
Solution Approach 2:
The fitting is designed as a sacrificial component that can be easily replaced rather than repaired. The simple construction with standard materials (metal fitting, rubber hose, vinyl tape) and basic assembly (insertion, threading, taping) makes it economical to replace as a unit when worn, avoiding the complexity of sophisticated stress relief devices that would require specialized maintenance and repair procedures.
3Strength
If full tensile strength stainless steel braiding is used, then burst strength is improved, but assembly torque requirement increases (exceeds 15 ft-lbs)
Solution Approach 1:
The patent changes the material parameter from full tensile strength stainless steel to less than full tensile strength stainless steel braiding. This parameter change reduces the burst strength slightly but dramatically reduces the assembly torque requirement to under 15 ft-lbs, making the assembly operationally easier while still meeting the required 5,000 psi burst strength specification.
4Reliability
If additional components are added for strain relief, then protection against mechanical wear is improved, but weight and cost increase
Solution Approach 1:
The strain relief function is merged into the fitting-hose assembly interface. The barbed insertion stem embedded in the hose end, combined with the clamping mechanism and vinyl tape wrapping, creates an integrated strain relief system. This eliminates the need for separate strain relief components while providing protection against mechanical wear through the combined structure.
Data Source
AI summary
A hose fitting assembly is provided, wherein the components are operably engaged with a length of hose to form a sacrificial construction. An end fitting having an insertion stem is disposed within a portion of the hose, wherein a clamping sleeve receiving a length of the hose threadingly engages the end fitting. A swaging collar is slide along the hose to threadingly engage the clamping sleeve, such that complete threaded engagement of the swaging collar and the clamping sleeve circumferentially compress and deform a portion of the clamping sleeve to clamp a portion of the hose intermediate the clamping sleeve and the insertion stem, and partially deformed threads on at least one of the clamping sleeve and the swaging collar. The hose fitting assembly can cooperatively engage a flexible high pressure metal braided hose, wherein the metal braid is formed of a less than full tensile strength steel, such as half hard stainless steel.