Undercut Anchor Expansion Sleeve With Levered Cutting Elements

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Solution Overview

Problem

Existing undercut anchors face challenges in optimizing the ratio of radial expansion force to axial force, leading to inefficiencies in expanding the expansion elements, which affects their anchoring effectiveness.

Innovation Solution

The undercut anchor features an expansion sleeve with cantilever elements that adapt to the expansion body's geometry, enhancing the leverage ratio by allowing the cutting edge to exert a greater radial force with reduced axial force, and includes a positive-lock coupling for rotational expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If conventional expansion elements are used without cantilever elements, then the structure is simpler, but the ratio of radial expansion force to axial force is lower, reducing anchoring effectiveness

Engineering Contradiction:
Improveradial expansion forceVSAvoidstructure complexity
Core Design Contradiction:
ForceVSDevice complexity

Solution Approach 1:

The expansion element is segmented into a base body and a separate cantilever element with a cutting element. This segmentation allows the cantilever element to act as a lever arm that amplifies the radial expansion force while the base body provides structural support, resolving the contradiction between force amplification and structural simplicity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The cantilever element acts as an intermediary between the expansion body and the cutting element. It transmits and amplifies the radial force from the expansion body to the cutting element, enabling greater radial expansion force with reduced axial force while maintaining a relatively simple overall structure.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If higher radial expansion force is applied to improve anchoring effectiveness, then the anchoring effectiveness increases, but the required axial force increases, reducing efficiency

Engineering Contradiction:
Improveanchoring effectivenessVSAvoidaxial force
Core Design Contradiction:
ReliabilityVSForce

Solution Approach 1:

The cantilever element extends in the axial dimension beyond the base body, creating a lever arm that operates in a different dimensional space. This allows the radial expansion force to be amplified through the lever arm effect, achieving higher anchoring effectiveness without proportionally increasing the axial force requirement.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The cutting element has a curved cutting edge that follows the conical surface of the expansion body. This curvature allows the cutting element to efficiently engage with the anchor hole wall and create an undercut, improving anchoring effectiveness while optimizing the force distribution between radial and axial components.

Inventive Principle:
Principle #14Spheroidality (Curvature)

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

This design improves the anchoring effectiveness by increasing the radial expansion force while reducing the required axial force, ensuring secure engagement in the anchor hole through a positive locking mechanism.

Implementation Method 1

The inner side of the cantilever element is supported on the expansion body during outward pivoting... enabling the leverage ratio to be enhanced by the cantilever element

Methodology Applied
Scientific EffectLever: Lever

Implementation Method 2

the expansion body is in particular frustoconical... arranged and designed such that when the expansion sleeve is displaced in the direction of the expansion body, it pivots the at least one expansion element at the front end of the expansion sleeve radially outwards

Methodology Applied
Scientific EffectMechanical Force: Mechanical Force

Implementation Method 3

the cutting element moves circumferentially around the longitudinal axis and in doing so creates the undercut in the anchor hole

Methodology Applied
Scientific EffectAbrasion: Abrasion

Data Source

PatentEP4402383B1Self-cutting undercut anchor
Publication Date: 2025.08.06 FISCHERWERKE ARTUR FISCHER GMBH & CO KG
  • EP4402383B1 patent drawingFigure 1~2
  • EP4402383B1 patent drawingFigure 3~6

AI summary

The invention proposes forming expansion elements (13) of an expansion sleeve (9) of a self-cutting undercut anchor (1) comprising forwardly projecting bracket elements (20) which can be pivoted outwards by bending such that they adapt to an "incline" of a frustoconical expansion body (7) of the undercut anchor (1) such that they rest flat against the expansion body (7), instead of resting thereagainst with a circumferential edge. The bracket elements (20) have a lever arm in relation to cutting edges (18) of the expansion elements (13), which lever arm increases an expansion force.