Press-Fit Double Pipe Spacer for Lower-Precision Assembly
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Solution Overview
Problem
The manufacturing of double pipes with spacers is costly due to the need for high dimensional precision in joining the inner, outer pipes, and spacers, which increases costs and complexity.
Innovation Solution
A double pipe design where the spacer is press-fitted between the inner and outer pipes, eliminating the need for precise abutment of spacer surfaces, and using a cylindrical spacer with a C-shaped opening to enhance heat transfer efficiency and stabilize the pipe shape during press-fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If blazing is used to join the inner pipe, outer pipe, and spacer, then the joining strength is improved, but the manufacturing precision requirement increases and manufacturing costs increase
Solution Approach 1:
The spacer is divided into two functional portions: a first portion with an abutment surface that contacts the inner pipe, and a second portion that is press-fitted into the outer pipe. This segmentation allows each portion to be optimized independently - the abutment surface can be precisely formed while the press-fit portion provides self-aligning tolerance compensation through interference fit.
Solution Approach 2:
The press-fitted second portion of the spacer acts as an intermediary mechanism between the inner pipe and outer pipe. It provides a self-aligning tolerance compensation function that eliminates the need for high-precision abutment surfaces, thereby reducing manufacturing costs while maintaining joining strength through the blazing process.
2Manufacturing precision
If high dimensional precision is achieved for spacer abutment surfaces, then the joining precision is improved, but the manufacturing costs increase
Solution Approach 1:
The spacer is segmented into a first portion containing the abutment surface and a second portion for press-fitting. This allows the abutment surface to be precisely formed on a smaller, more manageable portion while the second portion provides self-aligning tolerance compensation through interference fit, reducing overall manufacturing costs.
Solution Approach 2:
The invention changes the dimensional parameters of the spacer portions - the first portion has a smaller diameter than the outer pipe's inner diameter, creating a press-fit interference. This parameter change enables self-aligning tolerance compensation, reducing the need for high-precision abutment surfaces and lowering manufacturing costs.
3Use of energy by moving object
If the spacer has convex portions and concavity portions to increase heat exchange area, then the heat exchanging efficiency is improved, but the device complexity increases
Solution Approach 1:
The spacer features localized convex portions and concavity portions at specific locations to increase heat exchange area with the fluid, while the overall cylindrical structure with C-shaped opening maintains simplicity. The complex features are concentrated only where needed for heat exchange enhancement.
Solution Approach 2:
The spacer serves multiple functions: it maintains clearance between pipes, provides heat exchange surface area through convex/concave features, enables self-aligning tolerance compensation through press-fit design, and creates flow passages through its C-shaped opening. This multi-functionality reduces the need for additional components.
4Ease of manufacture
If the C-shaped opening is not inclined, then the manufacturing simplicity is improved, but the press-fitting process causes shape instability
Solution Approach 1:
The C-shaped opening is inclined at an angle rather than being perpendicular to the spacer axis, creating an asymmetric geometry. This asymmetry ensures that during press-fitting, the opening does not become pinched or deformed, maintaining shape stability while remaining manufacturable through standard processes.
Solution Approach 2:
The inclined opening geometry is designed in advance to prevent the harmful effect of pinching during press-fitting. By anticipating the deformation that would occur with a perpendicular opening, the design pre-compensates by angling the opening, thereby preventing shape instability before it occurs.
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 design reduces manufacturing costs by allowing for less precise assembly and improves heat transfer efficiency through the spacer, while maintaining the structural integrity and flow passage functionality of the double pipe.
Implementation Method 1
at least a part of the spacer is press-fitted by an inner circumferential surface of the outer pipe and by an outer circumferential surface of the inner pipe
Implementation Method 2
when a heated fluid is caused to flow through the pipe, the inner pipe can be heated by heat transfer
Data Source
AI summary
A double pipe includes an outer pipe in which an inner pipe is placed, and a spacer that maintains a clearance between the inner pipe and the outer pipe. At least a part of the spacer is press-fitted by an inner circumferential surface of the outer pipe and an outer circumferential surface of the inner pipe. More specifically, the outer pipe includes a diameter-reduced portion having undergone diameter reduction by plasticity processing. An inner circumferential surface of the diameter-reduced portion is present across the entire circumference other than the opening of the spacer, and presses an outer circumferential surface of the spacer inwardly in the radial direction.