Flexible Ferrule Structure for Lower-Torque Tube Assembly
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increasing strength of tubing materials requires stronger ferrule materials to grip and hold them, leading to higher assembly forces and torques, making proper assembly more difficult.
Innovation Solution
The development of ferrules with specific features such as a recessed bite edge, convex outer cam surfaces, and a reduced thickness portion near the nut end, which allows for easier assembly and improved grip, vibration resistance, and spring preload, by reducing the load and torque required during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stronger ferrule materials are used to grip stronger tubing materials, then the grip strength and holding capability are improved, but the assembly forces and torques required increase making proper assembly more difficult
Solution Approach 1:
The patent applies local quality by creating a bite edge with different material properties than the rest of the ferrule. The bite edge is work-hardened to higher hardness (e.g., 50-65 HRC) compared to the body (e.g., 30-45 HRC), allowing the localized gripping surface to be extremely hard for gripping stronger tubing while the overall ferrule remains more ductile and easier to assemble. This resolves the contradiction by concentrating the strength requirement only where needed for gripping.
Solution Approach 2:
The patent changes the material parameter (hardness) of the ferrule by applying differential heat treatment or work hardening processes. The bite edge undergoes parameters changes to achieve higher hardness through controlled deformation or thermal processing, while the body maintains lower hardness. This parameter differentiation allows the ferrule to provide strong gripping capability locally while maintaining overall ease of assembly.
2Strength
If ferrule materials become stronger to hold stronger tubing, then the gripping capability is improved, but the ferrule becomes less flexible and harder to assemble
Solution Approach 1:
The patent segments the ferrule into functionally distinct zones: a bite edge portion for gripping and a body portion for structural support and assembly. The bite edge is separated in terms of material properties through work hardening, allowing it to be independently optimized for gripping strength while the body remains optimized for assembly characteristics. This segmentation resolves the contradiction by decoupling the strength requirement from the overall ferrule structure.
Solution Approach 2:
The patent introduces dynamic characteristics by allowing the ferrule body to be more ductile and deformable during assembly, while the bite edge provides static high-strength gripping. The body can elastically deform to accommodate assembly variations and then spring back to maintain grip, creating a dynamic assembly process that works with rather than against the material strength.
3Reliability
If the ferrule is made from stronger materials, then the vibration resistance and fatigue life are improved, but the assembly torque required increases
Solution Approach 1:
The patent applies local quality by concentrating the high-strength, vibration-resistant material properties only at the bite edge where gripping and vibration resistance are critical. The body portion uses lower-strength material that requires less assembly torque. This localized application of strong material properties resolves the contradiction by providing vibration resistance only where needed rather than throughout the entire ferrule.
Solution Approach 2:
The patent creates a composite structure within the single ferrule component by combining two material states: work-hardened high-strength material at the bite edge and softer, more ductile material in the body. This internal composite structure allows the ferrule to exhibit both high vibration resistance (from the hard bite edge) and low assembly torque requirements (from the soft body).
Data Source
AI summary
A ferrule for coupling a tube to a fitting body of a fitting assembly. The ferrule may include a reduced thickness portion near a nut end of the ferrule, the reduced thickness portion being thinner than adjacent portions of the ferrule and configured to flex when the fitting assembly is made up. The ferrule may include a thin section toward the bite end of the ferrule, and an axially middle portion, between the thin section and the reduced thickness portion, may be configured to bow radially outwardly during assembly. The reduced thickness portion may have a radial thickness less than any other portion of the ferrule between the nut end and a bite edge of the ferrule closest to the nut end.