Brazed Tube Joint Assembly With Helical Protrusions for Centering
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Solution Overview
Problem
Conventional joining techniques face challenges in centering and retaining tube members, particularly in thin-walled structures, where knurling can lead to localized deformation and requires careful parameter control, and radiographic inspection may be necessary to ensure joint coverage.
Innovation Solution
A tube joint design featuring a second member with helical protrusions and bottom land surfaces that define a larger outer diameter, allowing for centering and retention within a first member's bore, using braze alloy, solder, or welding to secure the joint, eliminating the need for knurling and reducing the risk of braze voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If knurling is used to center and retain tube members, then the tube members can be retained within the bore, but localized thinning and thickening of the tube wall occurs requiring careful parameter control and potentially radiographic inspection
Solution Approach 1:
The continuous knurled surface is segmented into discrete helical protrusions separated by helical bottom land surfaces. This segmentation eliminates the need for continuous deformation, reducing localized thinning and thickening while maintaining the centering and retention functions. The discrete protrusions provide sufficient mechanical engagement without requiring precise control of knurling parameters across the entire surface.
Solution Approach 2:
Instead of applying knurling uniformly across the entire tube surface, the invention applies deformation only at specific locations where helical protrusions are formed. This localized approach concentrates the mechanical engagement at discrete points, reducing overall wall thickness variation while maintaining effective retention. The helical bottom land surfaces between protrusions provide smooth transitions that minimize stress concentration.
2Ease of operation
If knurling is applied to thin-walled structures, then centering and retention are achieved, but the localized thinning and thickening requires radiographic inspection to ensure joint coverage
Solution Approach 1:
The segmented helical protrusion design provides discrete mechanical engagement points that achieve centering and retention more reliably than continuous knurling. This reduces the variability in joint coverage, eliminating or reducing the need for radiographic inspection while maintaining ease of operation for thin-walled structures.
Solution Approach 2:
The helical protrusion design provides sufficient retention functionality without requiring the high precision and inspection protocols associated with traditional knurling. The simplified geometry allows for more tolerant manufacturing while achieving the same functional outcome, reducing both operational complexity and inspection requirements.
3Manufacturing precision
If helical protrusions are used instead of knurling, then the need for precise knurling parameter control is eliminated, but additional machining operations are required
Solution Approach 1:
The tube surface is prepared with a preliminary finish (such as a turned or ground surface) before forming the helical protrusions. This preliminary preparation provides a consistent base surface that simplifies the subsequent protrusion forming operation, reducing the overall manufacturing complexity despite the additional step. The preliminary action ensures uniform material properties and surface condition for the final feature formation.
Solution Approach 2:
The invention changes the manufacturing approach from continuous deformation (knurling) to discrete feature formation (helical protrusions). This parameter change in the manufacturing process allows for more tolerant dimensional control while achieving the same functional outcome, trading one type of manufacturing complexity for another that is more easily controlled.
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 provides a reliable and efficient method for centering and retaining tube members without the need for precise knurling, reducing the risk of braze voids and potentially eliminating the requirement for radiographic inspection, thereby enhancing the reliability and consistency of tube joint assemblies.
Implementation Method 1
Interference between the helical protrusion and bore of the first member can fix the second member within the bore of the first member.
Implementation Method 2
brazing typically involve flowing solder or braze between adjacent surfaces of the parts which, once solidified, forms a joint between the parts
Implementation Method 3
Welding generally involves fusing material from either (or both) parts to one another to form a joint between the parts
Data Source
AI summary
A tube joint includes a first member and a second member. The first member has a bore defining an inner diameter. The second member has a first outer surface defining a first outer diameter with two or more helical protrusions extending radially from the first outer diameter. The two or more helical protrusions collectively define a second outer diameter. The second outer diameter of the second member is larger than the inner diameter of the first member by an amount sufficient to center and retain the second member within the bore of the first member. Brazed tube joint assemblies and methods of making brazed tube joints are also described.