Undercut Anchor with Segmented Expansion Tabs
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Solution Overview
Problem
Existing fastening elements for anchoring in undercut boreholes often require high axial forces for expansion, which can damage thin components and may not securely transmit forces due to pressure on the borehole walls, and they lack effective anti-rotation mechanisms.
Innovation Solution
A fastening element with a conical expanding body and sleeve-shaped expansion element featuring radially outward expansion tabs with hinge-like bending points and a thin, arcuate engagement area, allowing for easy deformation and reduced pressure on the borehole wall, along with an anti-rotation device using a nose-like elevation and corresponding opening to prevent rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high axial forces are used to expand the expansion element in existing fastening elements, then the expansion element can securely anchor in the borehole, but thin components may be damaged and pressure on borehole walls increases
Solution Approach 1:
The expansion element is segmented into multiple expansion tabs that can be independently deformed. Each tab has a hinge-like bending point that allows controlled deformation, distributing the expansion force across multiple points rather than concentrating it, thereby reducing damage to thin components while maintaining anchoring security.
Solution Approach 2:
The patent changes the physical state and geometric parameters of the expansion element by introducing hinge-like bending points with reduced cross-sections. This allows the material to deform more easily at specific locations, reducing the axial force required for expansion while ensuring secure anchoring through controlled deformation into the undercut.
2Reliability
If high axial forces are applied to expand the expansion element, then anchoring is achieved, but the pressure on borehole walls increases causing potential damage
Solution Approach 1:
The expansion element is divided into multiple expansion tabs that distribute the anchoring force across several contact points on the borehole wall. This segmentation reduces the concentrated pressure on any single area of the borehole wall while maintaining overall anchoring security through the cumulative effect of multiple tabs.
Solution Approach 2:
The expansion element is designed to deform dynamically during installation, transitioning from a compact state to an expanded state that conforms to the borehole geometry. The hinge-like bending points enable controlled deformation that adapts to the borehole shape, reducing excessive pressure while ensuring secure anchoring.
3Strength
If the expansion element is made solid to ensure stability for force transmission, then force transmission capability improves, but the axial force required for expansion increases
Solution Approach 1:
The expansion element exhibits local quality variations through its hinge-like bending points, which have reduced cross-sections and lower material density in specific regions. These localized weak points require less force to deform, reducing the axial expansion force needed, while the remaining solid portions maintain sufficient strength for force transmission after expansion.
Solution Approach 2:
The expansion element is segmented into expansion tabs connected by hinge-like bending points. The tabs can be made sufficiently solid for force transmission, while the hinge regions use less material to enable easy deformation. This segmentation allows different parts of the same component to have different material densities and structural properties.
4Device complexity
If existing fastening elements lack anti-rotation mechanisms, then the structure remains simple, but rotation during nut tightening cannot be prevented
Solution Approach 1:
The anti-rotation device is merged with the expansion element itself, combining two functions (expansion and anti-rotation) into a single integrated component. The expansion tabs are formed with asymmetric geometries that provide both expansion capability and anti-rotation functionality, eliminating the need for separate anti-rotation mechanisms and maintaining structural simplicity.
Solution Approach 2:
The expansion element serves multiple functions: it provides expansion for anchoring, force transmission, and anti-rotation through its asymmetric tab geometries. This multi-functionality allows a single component to replace what would traditionally require multiple separate elements, maintaining simplicity while adding operational capabilities.
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
Enables secure anchoring with minimal axial force, protecting thin components from damage and ensuring stable force transmission, while preventing rotation during nut tightening, thus enhancing the fastening element's usability in thin components and reducing stress on borehole walls.
Implementation Method 1
The expansion tab has an opening in the form of an opening surrounded on all sides, which is arranged in particular in such a way that it reduces the cross section of the expansion tab in the region of its connection to the annular base body. The opening lies within the expansion flap, so that when the expansion flap is expanded, the opening is essentially moved outwards with the expansion flap.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a fastening element (1) for anchoring in an undercut drill hole. The fastening element (1) comprises a shank section (2) and an expanding element (3), wherein an expansion body (8) for expanding the expanding element (3) and a load-engaging means (7) are arranged on the shank section (2). The expanding element (3) is sleeve-shaped having an annular main body (13) at the rear end thereof in the direction of insertion (E), on which main body at the insertion end an expansion tab (10) having an opening (17) is arranged.