Resin Tube Fitting Using Differential Contraction Against Pullout
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Solution Overview
Problem
Resin tube fittings experience reduced resistance to forces pulling out the tube after undergoing heat cycles, as the materials used in existing designs do not effectively maintain grip during temperature changes.
Innovation Solution
The design incorporates an inner ring and union nut made of resin with a higher radial contraction rate for the connector compared to the press-in portion, ensuring increased friction and resistance when the fitting is cooled after being heated by fluid transfer, enhancing the holding force of the tube.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fitting uses conventional resin materials with uniform contraction properties, then the structure is simple and easy to manufacture, but the resistance to pullout force decreases after heat cycles
Solution Approach 1:
The patent applies local quality by making different portions of the fitting (inner ring and union nut) have different radial contraction rates. The connector portion is designed with a higher radial contraction rate than the press-in portion, allowing localized differential contraction behavior that increases friction and pullout resistance after heat cycles without requiring completely different materials throughout the entire fitting
Solution Approach 2:
The patent changes the physical parameter of radial contraction rate by selecting resins with different properties for the inner ring and union nut. The connector is designed to have a radial contraction rate higher by 0.05% or more than the press-in portion, creating parameter differentiation that generates the desired friction increase after thermal cycling
2Force
If the connector and press-in portion have the same radial contraction rate, then the material selection is simpler, but the friction force between tube and fitting is insufficient after cooling
Solution Approach 1:
Different resin materials are selected for the inner ring and union nut based on their specific functional requirements. The press-in portion uses resin optimized for insertion and initial gripping, while the connector uses resin with higher radial contraction to generate additional friction after cooling, creating local material optimization
Solution Approach 2:
The patent changes material parameters by selecting resins with different radial contraction rates. The connector's resin is chosen to have a higher radial contraction rate than the press-in portion's resin, creating parameter differentiation that directly increases the friction force after thermal cycling
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 configuration significantly increases the resistance to forces pulling out the tube by generating greater friction between the tube and the fitting, maintaining a higher grip even after repeated heat cycles.
Implementation Method 1
The inner ring and the union nut are made of resin, which has a property of contracting in response to change in ambient temperature. A radial contraction rate of the connector of the union nut is designed to be higher by 0.05% or more than that of the press-in portion of the inner ring.
Data Source
AI summary
A resin tube fitting has a body with a sleeve allowing the longitudinal end of the tube to be put therein, an inner ring with a press-in portion configured to be pressed in the longitudinal end of the tube, and a union nut with a connector configured to be screwed to an outer periphery of the body to allow the longitudinal end of the tube to be put radially between the connector and the press-in portion. The inner ring and the union nut are made of resin, which has a property of contracting in response to change in ambient temperature. The radial contraction rate of the connector is higher by 0.05% or more than that of the press-in portion of the inner ring.