Bi-Material Expansion Plug Structure for Sealing and Screw Guidance
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Solution Overview
Problem
Traditional single-material expansion plugs face issues with incomplete sealing, lateral screw deviation, and production defects like burr formation, which compromise anchoring stability and homogeneity.
Innovation Solution
An expansion plug made from two different thermoplastic materials, where a support body with expansion arms and a covering element are molded together, forming a thermochemical bond that enhances sealing and anchoring while preventing burr formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-material expansion plugs are used, then manufacturing is simple, but sealing performance is insufficient and anchoring is non-homogeneous
Solution Approach 1:
The expansion plug uses a bi-material construction with a hard support body (first material) and a soft covering element (second material). This composite structure combines the advantages of both materials: the hard material provides structural integrity and expansion force, while the soft material ensures complete sealing contact with the wall hole. This resolves the contradiction by achieving superior sealing performance through material composition rather than simple single-material design.
Solution Approach 2:
Different regions of the expansion plug are made from materials with different properties. The support body uses hard material for structural functions, while the covering element uses soft material for sealing functions. This local differentiation of material quality allows each part to optimize its specific function, achieving homogeneous anchoring and complete sealing without requiring the entire plug to be complex.
2Reliability
If two different plastic materials are used separately, then sealing is improved, but surface area of sealing zone decreases and inhomogeneity increases
Solution Approach 1:
The soft covering element is molded directly onto the hard support body, merging the two materials into a single integrated component. This combination maintains the large sealing surface area of the entire plug exterior while ensuring complete sealing contact. The merged structure eliminates the separation issue of prior art, providing both high sealing performance and sufficient sealing zone surface area simultaneously.
Solution Approach 2:
The bi-material composite structure allows the soft covering element to conform to the wall hole surface while the hard support body provides structural support. This composite design ensures the entire external surface of the plug contributes to sealing, maintaining large sealing zone surface area while achieving complete sealing contact through the soft material's adaptability.
3Ease of manufacture
If axial groove is formed in inner part, then material flow is improved, but burr formation occurs during production
Solution Approach 1:
The axial groove is pre-formed in the hard support body before the soft covering element is molded onto it. This preliminary action allows the groove to be created when the material is still in a controllable state, enabling complete material flow into the groove without trapping air or creating burrs. The groove geometry is optimized to guide material flow smoothly, preventing defect formation during the molding process.
Solution Approach 2:
The axial groove dimensions and geometry are carefully controlled with specific parameter ranges to optimize material flow. The groove width, depth, and taper angle are designed to allow complete filling of the hard material without creating burrs or voids. This parameter optimization resolves the contradiction by achieving both improved material flow and elimination of burr formation.
4Ease of operation
If screw insertion is performed without guidance, then installation is simple, but lateral deviation occurs compromising correct installation
Solution Approach 1:
The soft covering element acts as an intermediary between the screw and the wall hole. Its compliant nature allows it to deform and guide the screw into correct alignment during insertion. The covering element's friction characteristics and geometric profile provide natural guidance that prevents lateral deviation, achieving both simple installation and high installation precision simultaneously.
Solution Approach 2:
The soft covering element functions as a flexible shell that deforms during screw insertion to provide guidance. Its flexibility allows it to accommodate minor misalignments and guide the screw into the correct position, while its structural integrity prevents excessive deformation. This flexible shell approach resolves the contradiction by enabling self-guiding installation without complex alignment procedures.
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 bi-material expansion plug achieves stable and homogeneous anchoring with high sealing performance on various materials, prevents lateral screw deviation, and reduces production defects, ensuring reliable fastening and reduced waste.
Implementation Method 1
an expansion plug made from two different thermoplastic materials, where a support body with expansion arms and a covering element are molded together, forming a thermochemical bond
Data Source
Figure 1
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AI summary
An expansion plug comprising: a support body (12) made of a first thermoplastic material, having two expansion arms (20) extending between a collar (16) and a terminal (18), and wherein two windows (22) are formed between the two expansion arms (20) and are opposite each other, and a covering element (34) made of a second thermoplastic material overmolded on the support body (12), having two filling portions (36) each of which fills a respective window (22), wherein the filling portions (36) have respective grooves (38) open along external sides of the expansion plug (10) and separated from the central cavity (14) by respective membranes (40) configured to break during the screwing of a screw.