Expansion Anchor Without Sliding Coating
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Solution Overview
Problem
Existing expansion anchors require a sliding coating for effective anchoring in tensile zones, which increases manufacturing effort and quality assurance complexity, and may not maintain stability over time due to crack expansion and contraction in building materials like concrete.
Innovation Solution
A metal expansion anchor design without a sliding coating, featuring a conical expansion body and sleeve with specific geometric parameters, including varying wall thicknesses and cone angles, allowing for self-expansion and secure anchoring through frictional forces, facilitated by a diameter step and inclined extension for enhanced sliding and penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sliding coating is applied to the expansion sleeve and/or expansion body, then reliable sliding function and corrosion protection are achieved, but manufacturing effort and quality assurance complexity increase
Solution Approach 1:
The invention extracts and eliminates the sliding coating from the expansion anchor system. Instead of applying a separate coating layer, the expansion sleeve is designed with a specific geometric feature (extension with reduced wall thickness and inclined inner surface) that inherently provides the sliding function without requiring additional coating materials or application processes.
Solution Approach 2:
The expansion sleeve's extension acts as a self-contained sliding mechanism. The inclined inner surface of the extension (with angle α between 5° and 15°) automatically provides the necessary sliding properties through its geometry alone, making the system self-sufficient without external coatings.
2Reliability
If a sliding coating is applied to ensure long-term stability, then anchoring reliability under crack expansion is improved, but quality assurance effort increases
Solution Approach 1:
The invention removes the sliding coating requirement entirely, replacing it with a geometric solution. The extension's inclined surface provides consistent sliding properties that do not degrade over time, eliminating the need for quality assurance of coating thickness and adhesion.
Solution Approach 2:
The invention changes the approach from chemical/coating-based sliding (requiring thickness control) to geometric-based sliding. By defining the inner surface angle α of the extension between 5° and 15°, the sliding function is achieved through a single geometric parameter that is easier to control and verify during manufacturing.
3Ease of manufacture
If the expansion sleeve has uniform wall thickness, then manufacturing is simplified, but effective expansion and anchoring in tensile zones is compromised
Solution Approach 1:
The invention applies local quality by creating a non-uniform wall thickness distribution in the expansion sleeve. The extension at the front end has reduced wall thickness compared to the base body, with the inner surface of the extension inclined at angle α. This localized geometric modification provides enhanced sliding and expansion capabilities precisely where needed during insertion and loading.
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 design ensures reliable expansion and anchoring without a sliding coating, reducing manufacturing effort and potential errors, while maintaining secure hold even under load changes and crack expansion, ensuring long-term stability without the need for additional coatings.
Implementation Method 1
allowing for self-expansion and secure anchoring through frictional forces
Implementation Method 2
The inside of the extension is inclined to the longitudinal axis of the expansion anchor, so it widens conically with a second cone angle, whereby here 'conical' does not mean strictly mathematically frustoconical
Data Source
Figure 1
Figure 2~4
AI summary
The invention relates to a metal expansion anchor. Such expansion anchors currently have a sliding coating to ensure re-expansion, particularly in cracked concrete. To avoid the associated manufacturing effort, the invention proposes omitting the sliding coating. Surprisingly, it was found that reliable re-expansion still occurs when certain geometric parameters are maintained.