Expansion Bolt with Multi-Segment Sleeve for Higher Holding Force

Solution Overview

Problem

Existing expanding socket-coated connecting bolts used in wood fiber board connections have suboptimal holding force under tensile loads due to two expandable socket segments that only spread in two directions, and their production with slide-less injection molding tools is inefficient.

Innovation Solution

The socket end surrounding the bolt cone is divided into at least three segments with non-parallel slots, allowing for a more even force distribution and higher angular stability, enabling higher extraction forces, and allowing for cost-effective production using slide-less injection molding tools.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the sleeve end is divided into two expandable sleeve segments by two parallel slots, then the manufacturing is simpler with slideless injection molding tools, but the holding force under tensile load is not optimal

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidholding force

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The expansion sleeve is divided into multiple sleeve segments (at least three) by slots, allowing the sleeve to expand in multiple directions when the bolt is tightened. This segmentation enables the sleeve to engage more effectively with the bore walls, significantly improving the holding force under tensile load compared to having only two segments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The slots separating the sleeve segments are designed to be non-parallel to the bolt axis, creating an asymmetric expansion pattern. This asymmetric slot configuration allows the sleeve segments to spread at angles, providing better engagement with the bore walls in multiple directions, thereby enhancing the holding force while remaining compatible with slideless injection molding tools.

Inventive Principle:

Principle #4Asymmetry

2Strength

If the sleeve end is divided into three or four sleeve segments, then the holding force and angular stability are higher, but the manufacturing complexity increases requiring injection molds with slides

Engineering Contradiction:

Improveholding forceVSAvoidmolding tool complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The expansion sleeve is divided into multiple sleeve segments (at least three) by slots, allowing the sleeve to expand in multiple directions when the bolt is tightened. This segmentation enables the sleeve to engage more effectively with the bore walls, significantly improving the holding force under tensile load compared to having only two segments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The slots separating the sleeve segments are designed to be non-parallel to the bolt axis, creating an asymmetric expansion pattern. This asymmetric slot configuration allows the sleeve segments to spread at angles, providing better engagement with the bore walls in multiple directions, thereby enhancing the holding force while remaining compatible with slideless injection molding tools.

Inventive Principle:

Principle #4Asymmetry

3Ease of manufacture

If the slots run parallel to the bolt axis, then the manufacturing with slideless injection molding tools is cost-effective, but the force distribution in the bore is not uniform

Engineering Contradiction:

Improvemanufacturing cost-effectivenessVSAvoidforce distribution uniformity

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The slots separating the sleeve segments are designed to be non-parallel to the bolt axis, creating an asymmetric expansion pattern. This asymmetric slot configuration allows the sleeve segments to spread at angles, providing better engagement with the bore walls in multiple directions, thereby enhancing the holding force while remaining compatible with slideless injection molding tools.

Inventive Principle:

Principle #4Asymmetry

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 solution achieves a higher holding force and more even force distribution in wood fiber board connections under tensile loads, enhancing angular stability and extraction forces while simplifying the production process.

Implementation Method 1

When the dowel element moves longitudinally relative to the sleeve element in a first direction, the expansion area engages with the expandable section, causing the expandable section to move laterally outwards.

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Data Source

PatentEP3353428B1Connecting expansion bolts over-moulded with expansion sleeves

Publication Date: 2019.06.12 HAFELE BERLIN GMBH & CO KG

Figure 1~3
Figure 4~6

AI summary

The invention relates to a connecting expansion bolt (1) over-moulded with an expansion sleeve, comprising a bolt head (3) on one bolt end and a bolt cone (4: 15a, 15b) on the other bolt end, tapering in the direction of the bolt head (3), wherein the bolt cone (4: 15a, 15b) and a bolt shaft section (6) connecting thereto are over-moulded with a plastic expansion sleeve (5), the sleeve end (9) thereof surrounding the bolt cone (4: 15a, 15b) being divided by open slits (10) in the end into multiple expandable sleeve segments (11). According to the invention, the sleeve end (9) surrounding the bolt cone (4: 15a, 15b) is divided into at least three sleeve segments (11), and at least two of the slits (10) on the bolt cone (4: 15a, 15b) separating the sleeve segments (11) from one another do not run parallel to the bolt axis (7).