Expansion Dowel Structure for High Extraction Resistance
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Solution Overview
Problem
Existing expansion attachment dowels offer only moderate resistance to extraction from the hole following installation, and they do not provide stable and secure axial attachment.
Innovation Solution
The dowel features a substantially cylindrical anchoring body with Y-shaped notches that expand radially upon screwing, allowing for secure and stable axial attachment, with expandable elements that can expand up to 50% of the dowel's diameter without breaking, and include radial ridges for enhanced contact with the wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional expansion dowels are used, then the dowel can be inserted into the wall, but the resistance to extraction is only moderate
Solution Approach 1:
The dowel body is divided into multiple expandable elements separated by notches, allowing each element to expand independently and create multiple anchoring points along the dowel length, significantly increasing extraction resistance
Solution Approach 2:
The expandable elements feature radial ridges that extend outward from the dowel surface, adding a radial dimension to the anchoring mechanism. This radial expansion creates friction and mechanical interlocking with the wall material, transforming the anchoring from purely axial to multi-dimensional
2Strength
If the expandable elements expand radially, then the grip in the hole is improved, but the dowel may break in marginally loose materials
Solution Approach 1:
The dowel is segmented into multiple independent expandable elements, distributing the expansion stress across numerous small elements rather than one large element, reducing the risk of catastrophic failure
Solution Approach 2:
The geometric parameters of the expandable elements are optimized to control expansion magnitude and stress distribution, allowing sufficient grip while preventing material failure through carefully designed ridge profiles and notch configurations
3Stability of the object's composition
If the dowel is designed for axial anchorage, then rotation and axial movement are prevented, but the complexity of the dowel structure increases
Solution Approach 1:
The dowel transitions from a static structure to a dynamic one, where the expandable elements can change shape in response to screw insertion, automatically creating axial anchorage features without requiring complex pre-formed structures
Solution Approach 2:
The dowel creates its own axial anchorage features through the expansion action itself, where the radial expansion of elements with longitudinal ridges automatically generates the mechanical interlocking needed to prevent rotation and axial movement, without requiring separate components
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 dowel provides high resistance to extraction forces, ranging from 15 kN to 20 kN, ensuring secure and stable attachment over time, even in varying wall materials.
Implementation Method 1
The expandable elements, as a result of the screwing of the screw, expand radially to anchor, during use, in the installation hole made in the wall
Implementation Method 2
one or more of the expandable elements are provided with radial ridges... so as to improve the contact of the expandable element with the wall of the installation hole
Data Source
Figure 1~3
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Figure 8~9
AI summary
Expansion attachment dowel comprising an anchoring body (11) with a substantially cylindrical shape and provided with an axial cavity (14) that develops along a longitudinal axis (X). The anchoring body (11) comprises a plurality of attachment elements (17) radially expandable toward the outside of the anchoring body (11) and defined by a corresponding plurality of notches (16) through toward the axial cavity (14).