Tube-to-Panel Interference Assembly Without a Mandrel
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Solution Overview
Problem
Conventional methods for forming a joint between a tube and a panel using an interference fit are challenging when the tube diameter is less than that of the mandrel, leading to complex and costly processes, especially in high-volume production.
Innovation Solution
A method involving punching a hole in the panel with a smaller diameter than the tube, preforming the tube end to generate a flare or flange, and applying axial force to achieve an interference fit between the tube and the panel, eliminating the need for a mandrel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a mandrel is used to form the interference fit between tube and panel, then the joint strength is achieved, but the process complexity and cost increase when tube diameter is less than mandrel diameter
Solution Approach 1:
The patent removes the mandrel from the assembly process entirely. Instead of inserting a mandrel into the tube to expand it, the tube is directly inserted into the panel hole and expanded by the interference fit itself, eliminating the need for mandrel handling and setup
Solution Approach 2:
The tube end is preformed (flared or flanged) before insertion into the panel. This preliminary shaping allows the tube to be inserted without a mandrel while still achieving the necessary expansion and secure fit, simplifying the overall process
2Strength
If a mandrel is used to expand the tube for interference fit, then the joint is secured, but additional setup and handling requirements increase production costs
Solution Approach 1:
The mandrel is completely removed from the process, eliminating the need for specialized mandrel handling equipment and setup procedures, thereby reducing manufacturing complexity and cost
Solution Approach 2:
The tube itself performs the expansion function that previously required a mandrel. The interference fit between the tube and panel hole causes the tube to expand and secure the joint without external assistance
3Device complexity
If the tube diameter is made smaller than the panel hole to avoid mandrel use, then process simplicity increases, but the interference fit strength decreases
Solution Approach 1:
The tube end is preformed (flared or flanged) before insertion. This preliminary action allows the tube to be inserted into the panel without requiring the tube diameter to be smaller than the hole, while still achieving strong interference fit as the tube expands during insertion
Solution Approach 2:
The tube diameter is made slightly larger than the panel hole diameter (0.25 inch tube vs. 0.244 inch hole), creating a positive interference fit. The preformed tube end enables this larger diameter to be inserted while maintaining process simplicity
4Productivity
If high-volume production is implemented with conventional mandrel methods, then production volume increases, but setup complexity and costs increase
Solution Approach 1:
The mandrel is removed from the high-volume production process, eliminating the need for complex mandrel handling setups and reducing the complexity associated with high-volume production
Solution Approach 2:
Each tube performs its own expansion and securing function through the interference fit mechanism, without requiring external mandrels or complex setup equipment, enabling simplified high-volume production
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 method efficiently forms a rigid joint with reduced material stress and cost, enabling high-volume production without additional setup, while maintaining joint strength and allowing for heat treatment without compromising the assembly's integrity.
Implementation Method 1
preforming a first end of the tube to generate a flare or a flange
Implementation Method 2
application of axial force on the tube until the preformed first end of the tube abuts a periphery of the hole of the panel... achieving an interference fit between the hole of the panel and the tube
Data Source
AI summary
A method of forming an assembly between a panel and a tube includes forming a hole in the panel, where a diameter of the hole is smaller than an outer diameter of the tube, and preforming a first end of the tube to conceal the hole of the panel. A diameter of the preformed portion is greater than the diameter of the hole and the outer diameter of the tube. The method further includes aligning a second end of the tube with the hole of the panel, followed by inserting the tube into the hole by application of axial force on the tube until the preformed first end of the tube abuts a periphery of the hole of the panel. The method also includes achieving an interference fit between the hole of the panel and the tube.