Double-Walled Corrugated Pipe End Profile for Watertight Welding
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Solution Overview
Problem
The existing methods for welding corrugated pipes with double walls face challenges in forming a stable and watertight joint due to deformation of ribbings and trapped air during the injection of the external sleeve, which requires complex and burdensome operations like removing radial corrugations.
Innovation Solution
A specific cut shaping of the pipe end, comprising a cylindrical ring on the internal wall and a radial ring on the external wall, both cut simultaneously, creates a large, stable adhesion surface that prevents air trapping and ensures a solid weld without subsequent machining, using a pack of cutting disks and a coaxial mill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radial corrugations are removed with a mill to prevent air trapping, then the weld quality improves, but the device complexity and manufacturing burden increase
Solution Approach 1:
The patent applies preliminary action by designing the cut shaping to inherently prevent air trapping during injection, eliminating the need for subsequent corrugation removal. The specific cut geometry (with the internal wall cut perpendicular to the axis and external wall cut at an angle) is prepared in advance during pipe manufacturing, so that when injection occurs, air is naturally directed toward the end of the pipe rather than being trapped between corrugations and the injected material.
Solution Approach 2:
The patent extracts the problematic radial corrugations from the injection zone by positioning the cut shaping such that the external wall cut removes the outermost corrugation development. This extraction eliminates the source of air trapping while maintaining the structural integrity of the pipe, allowing injection to proceed without complex post-processing operations.
2Strength
If a large adhesion surface is created for welding, then the joint strength improves, but the risk of air trapping increases
Solution Approach 1:
The patent applies local quality by creating different cut geometries for the internal and external walls. The internal wall is cut perpendicular to the axis to maximize adhesion surface area, while the external wall is cut at an angle to direct air flow away from the injection zone. This localized differentiation of cut quality allows the system to simultaneously achieve large adhesion surface and prevent air trapping.
Solution Approach 2:
The specific cut shaping acts as an intermediary element between the injection material and the pipe structure. The angled external wall cut serves as a mediator that guides air flow toward the pipe end, preventing direct contact between trapped air and the adhesion zone, thereby allowing large surface area welding without air interference.
3Reliability
If complex machining operations are performed to prepare the pipe end, then the weld reliability improves, but the productivity decreases
Solution Approach 1:
The patent implements preliminary action by incorporating the precise cut shaping directly into the pipe manufacturing process. The internal and external wall cuts are performed during pipe production rather than as separate post-processing operations, ensuring the correct geometry is already in place before injection, thereby maintaining high reliability without reducing productivity.
Data Source
Figure 1~2a
Figure 3
AI summary
A profile (5), obtained by cutting, of the end of a corrugated pipe (2) with double wall, in a plastic material of the polyolefin type, to form the weld of an external bell or sleeve (1), cylindrical internally, also in a plastic material of the polyolefin type, injected in situ and positioned axially to the pipe, in order to form a joint (3) of the corrugated pipe itself; this profile (5) being composed of a first ring (6) obtained by a cut perpendicular to the axis of the pipe in the section of internal cylindrical wall (20), intermediate in relation to the axial development of a single corrugation (22) formed by the external wall (21) and by a second ring (7), adjacent to the first, and obtained by a cut combined with the previous one and performed on the wall of the corrugation itself, on its rising section with more radial trend from the centre towards the periphery, with removal of its outermost zone.