Electrofusion Fitting Radial Expansion for Pipe Welding
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Solution Overview
Problem
Large diameter pipes made of thermoplastic materials face challenges in electric welding due to significant gaps and ovality, leading to cavitation and blowholes in the weld zone, which compromise the strength of the weld joint.
Innovation Solution
An electric welding coupler with a reinforcing ring around the outer circumference of a cylindrical body, which restricts expansion and applies pressure to the inner circumference, reducing the annular gap and using a liquid-filled cavity to generate pressure for effective welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pipe diameter is increased, then the corrosion resistance and weight reduction benefits improve, but the gap between pipeline and coupler increases making optimal welding difficult to achieve
Solution Approach 1:
The coupler incorporates a expandable structure with radial expansion capability. The coupler body can dynamically adjust its internal diameter through radial expansion to accommodate pipes of varying diameters and ovality, transforming a static gap problem into a dynamic solution where the coupler adapts to the pipe dimensions rather than requiring precise pre-matching of dimensions.
2Manufacturing precision
If production tolerances are narrowed to reduce gap formation, then welding precision improves, but the difficulty of introducing the pipe into the coupler increases due to ovality
Solution Approach 1:
The coupler features a dynamic expansion mechanism that allows the internal diameter to increase radially during the insertion phase, facilitating easy pipe introduction even with ovality. After insertion, the coupler maintains the reduced gap configuration for optimal welding, thus providing ease of operation during insertion while achieving manufacturing precision during welding.
Solution Approach 2:
The coupler is designed to perform the expansion action preliminarily before the welding process begins. By expanding the coupler internally to accommodate the pipe with ovality first, and then maintaining the proper gap configuration for welding, the system prepares the optimal welding condition in advance while eliminating insertion difficulties.
3Reliability
If high pressure is applied to eliminate cavitation, then blowhole formation is reduced, but the device complexity increases
Solution Approach 1:
The coupler utilizes the heat generated during the welding process itself to cause thermal expansion of the plastic material. This self-generated thermal expansion automatically applies the necessary pressure to eliminate cavitation and prevent blowhole formation, without requiring external pressure application mechanisms. The welding heat serves dual purposes: melting the plastic for bonding and simultaneously pressurizing the material to prevent voids.
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 solution ensures a strong weld joint by minimizing the amount of melt needed, reducing heating time, and minimizing the cold zone, thereby preventing blowholes and enhancing the structural integrity of the weld.
Implementation Method 1
containing at least one welding element; wherein the welding element is arranged close to the inner diameter of the cylindrical body, wherein the welding element forms at least two weld zones, a contact for feeding the electric current
Implementation Method 2
DE 38 08 229 A1 discloses a sleeve with incorporated heating wires for welding plastic pipes lying with their ends opposite one another, there is formed on the outer circumference of the region of the sleeve provided with heating wires at least one closed chamber, in which the air becomes warmer during heating up of the heating wires, so that a radially inwardly directed pressure is produced by the volume expansion.
Implementation Method 3
The resin on the interior of the welding socket is semi-molten with the electric heating wire
Data Source
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AI summary
Electric welding coupler (1) for the welding of pipes made of thermoplastic material or other weldable plastics comprising a cylindrical body (2) made of thermoplastic material or other weldable plastics, containing at least one welding element (3), wherein the welding element (3) is arranged close to the inner diameter of the cylindrical body (2), wherein the welding element (3) forms at least two welding zones (15), a contact (13) for feeding the electric current and at least one cavity (5), wherein the cavity (5) is arranged in the cylindrical body (2), wherein a reinforcing ring (6) is arranged around the outer circumference (7) respectively outer diameter of the cylindrical body (2).