Curved Double Pipe Manufacturing Without Liquid Nitrogen
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Solution Overview
Problem
Existing methods for manufacturing curved double pipes, such as those used in catalytic converters, face challenges in maintaining a reliable air space between the inner and outer pipes due to flattening issues when bending straight pipes, and require costly equipment and labor with the use of pressurized liquid nitrogen.
Innovation Solution
A method involving drawing a plate into a curved U-shape, inserting and welding an inner pipe, and bending the half pipe to form a circular cross-section around the inner pipe, eliminating the need for ice and liquid nitrogen, thus avoiding flattening and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a straight double pipe is simply bent to form a curved shape, then the manufacturing process is simple, but the curved portion becomes flattened and the prescribed air space cannot be reliably formed between the inner pipe and outer pipe
Solution Approach 1:
The patent applies preliminary action by pre-freezing water inside the straight double pipe to form ice before bending. This ice core provides internal support that prevents flattening during the bending process, ensuring the air space is maintained. The freezing step is performed in advance of the bending operation, allowing the pipe to be shaped while preserving the critical air gap dimensions.
Solution Approach 2:
The patent uses ice as an intermediary substance inside the pipe during bending. The ice acts as a temporary support structure that mediates between the bending force and the pipe walls, preventing excessive deformation and flattening. After bending is complete, the ice is melted and removed, leaving the pipe in its curved shape with the air space intact.
2Productivity
If pressurized liquid nitrogen is used to quickly freeze water and form ice inside the double pipe, then the bending process can be performed, but additional equipment and material costs are incurred due to the use of pressurized liquid nitrogen
Solution Approach 1:
The patent replaces expensive pressurized liquid nitrogen with ordinary water as the freezing medium. Water is a cheap, readily available substance that can be frozen using simple refrigeration equipment. The water serves its purpose as a temporary support during bending, then melts and is drained away, eliminating the need for costly cryogenic materials and specialized handling equipment.
Solution Approach 2:
The patent employs a self-service approach where the water inside the pipe serves multiple functions: it provides the mass needed for freezing, acts as the freezing medium itself, and after melting, serves as the drainage fluid. This eliminates the need for separate systems to introduce and remove freezing agents, simplifying the overall equipment requirements.
3Productivity
If pressurized liquid nitrogen is used for freezing, then quick freezing is achieved, but additional labor costs are incurred for managing and handling the liquid nitrogen
Solution Approach 1:
The patent replaces complex-to-handle pressurized liquid nitrogen with ordinary water that can be frozen using standard refrigeration. Water requires no special handling procedures, storage tanks, or safety protocols associated with cryogenic materials. The water is introduced in liquid form, frozen in place, and after use, melts and drains automatically, eliminating all manual handling operations.
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 allows for the cost-effective and reliable manufacturing of curved double pipes with a consistent annular gap, improving insulation and simplifying the manufacturing process without the need for expensive equipment or labor-intensive handling of liquid nitrogen.
Implementation Method 1
drawing a plate (1), which has a predetermined planar shape that at least substantially corresponds to a desired final shape of a curved outer pipe (4), into a curved, substantially U-shape in cross-section
Implementation Method 2
welding together the inner pipe (3) and the half pipe (curved U-shaped intermediate part) (2) at one longitudinal end thereof
Implementation Method 3
bending (curving or curling) longitudinally-extending edges of the half pipe (curved U-shaped intermediate part) (2) so as to cause the longitudinal edges to abut (touch), whereby a substantially circular cross-section is formed
Data Source
AI summary
A method for manufacturing a double pipe includes: drawing a plate (1), which has a predetermined shape corresponding to the desired final shape of a curved outer pipe (4), into a curved, substantially U-shape in cross-section to produce a half pipe (2). Then, an inner pipe (3), which has a curved shape similar to the desired final curved shape of the outer pipe, is inserted into and positioned within the interior space of the half pipe. Subsequently, the inner pipe is welded to the half pipe at one longitudinal end thereof. Thereafter, longitudinally-extending edges of the half pipe are curled towards each other until they abut and a substantially circular cross-section is formed that surrounds the exterior of the inner pipe. The abutting longitudinally-extending edges (22) of the half pipe are then welded together to produce the curved outer pipe (4).