Spin-Welded Fixing Plug for Tear-Resistant Plastic Panels
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Solution Overview
Problem
The plastic core in sandwich panels used for various applications, such as vehicle walls, is not compatible with direct screw fixation due to low resistance to tearing, and existing dowel systems with projecting threads do not provide sufficient resistance for most applications.
Innovation Solution
A fixing pin with a frustoconical welding body, featuring a smooth blind central bore and a conical centering point, is used for rotational welding into the plastic panel, providing enhanced friction and rigidity, allowing for strong and quick fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If direct screw fixation is used in the plastic core, then the installation is simple, but the resistance to tearing is very low
Solution Approach 1:
The patent applies preliminary action by first inserting a welding plug into the plastic core before screw fixation. The plug is rotatively welded into the core to create a reinforced anchoring point, and only then is the screw fixed into the plug. This preliminary reinforcement step resolves the contradiction by providing both structural strength for tearing resistance and maintaining operational simplicity through a standardized two-step process.
2Strength
If anchors with prominent threads are used, then the resistance to tearing is slightly improved, but it remains insufficient for most applications
Solution Approach 1:
The patent employs composite materials by combining the welding plug (made of plastic material compatible with the core) and the screw (metal or other material) into a unified fastening system. The plug acts as an intermediate composite element that distributes mechanical stresses between the screw and the plastic core, significantly improving tearing resistance while maintaining relatively simple individual component structures.
Solution Approach 2:
The welding plug features a frustoconical shape with a specific apex angle (24°-25°) that optimizes friction and welding effectiveness. This curved conical geometry allows the plug to be rotatively welded into the core with excellent mechanical interlocking, providing superior tearing resistance without requiring complex threaded structures in the plug itself.
3Strength
If a frustoconical shape with apex angle of 24°-25° is used, then the friction between anchor and substrate is particularly effective, but the manufacturing precision requirement increases
Solution Approach 1:
The patent specifies a narrow parameter range (24°-25° apex angle) to optimize the balance between friction effectiveness and manufacturability. This parameter optimization ensures that the conical surface generates sufficient friction during rotative welding while remaining compatible with standard manufacturing tolerances. The specific angle range represents a compromise that achieves particularly effective friction without requiring excessively tight manufacturing precision.
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 achieves excellent resistance to tearing and allows for secure attachment of objects to the panel, enabling the use of self-tapping screws without risk of the pin being torn from the panel during tightening.
Implementation Method 1
the friction between the frustoconical outer face of the fixing body and the material constituting the support causes the simultaneous melting of a superficial layer of the outer face of the fixing body and the material in contact with the support
Implementation Method 2
the friction between the frustoconical outer face of the fixing body and the material constituting the support causes the simultaneous melting of a superficial layer of the outer face of the fixing body and the material in contact with the support, the molten materials of the fixing plug and the support mixing
Implementation Method 3
a cooling step which occurs when the large base of the fixing body is substantially flush with the face of the support, during which the rotation is interrupted so that the mixture of molten plastic material solidifies to achieve the welding fixing of the fixing plug in the support
Data Source
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AI summary
The invention relates to a fixing dowel (16) which is intended to be fixed by rotational welding in an orifice (18) of a support (10) made of plastic material, the fixing dowel (16) comprising a body (22) for welding which has an external face (24) of frustoconical shape of revolution about a principal axis (A) which extends from a large base (26) intended to be flush with a surface of the support (10), to a small base (28) intended to be driven axially into the orifice (18) of the support (10).