Eccentric Connection Bolt for Gap-Free Furniture Panel Butt Joints

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Solution Overview

Problem

Existing connecting bolts for furniture panels made of chipboard, MDF, or wood-like materials often result in gaps between parts due to misalignment, leading to instability and aesthetic issues, as the axis of rotation is not accurately positioned at the edge of the hole, causing gaps between the butt joint and bore wall.

Innovation Solution

A connecting bolt design with an axially offset bolt head and a barb-like clamping structure on the shank, featuring a radially projecting blade-shaped projection and a concave web to secure the bolt head into the bore, ensuring a gap-free and stable connection by defining the axis of rotation at the edge of the hole and preventing the bolt from being pulled out.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the axis of rotation is positioned at the bore edge, then a gap-free connection is achieved, but the manufacturing precision is difficult to control

Engineering Contradiction:
Improvepositioning precision of axis of rotationVSAvoidease of positioning axis of rotation
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The axis of rotation is pre-positioned at the bore edge through the eccentric design of the bolt head relative to the bolt shaft. This preliminary positioning ensures that when the first part is inserted at an angle and pivoted, the rotation axis is already correctly located, eliminating the need for subsequent adjustment and ensuring gap-free connection without complicating the manufacturing process

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The bolt head is designed with an eccentric offset relative to the bolt shaft, creating an asymmetric structure. This asymmetry causes the axis of rotation to be naturally positioned at the bore edge during the pivoting motion, rather than requiring symmetric alignment. The asymmetric design simplifies the manufacturing process while achieving precise positioning

Inventive Principle:
Principle #4Asymmetry

2Strength

If the projection is made sharp for penetrating the bore wall, then anchoring strength is improved, but the projection becomes susceptible to plastic deformation

Engineering Contradiction:
Improveanchoring strength of projectionVSAvoidresistance to plastic deformation of projection
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The web connecting the projection to the head section is designed with a concave outer contour that compresses the material in the second part during pivoting. This pre-compression creates a cushioning effect that supports the sharp projection, preventing it from undergoing plastic deformation while maintaining its ability to penetrate and anchor in the bore wall

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The web acts as an intermediary structure between the projection and the head section. Its concave contour design allows it to compress the material in the second part, providing indirect support to the projection. This intermediary action protects the sharp projection from direct deformation forces while maintaining anchoring strength

Inventive Principle:
Principle #24Intermediary (Mediator)

Data Source

PatentEP3821142B1Connection bolt for tool-free butt-joining of two furniture panels
Publication Date: 2022.01.05 HAFELE BERLIN GMBH & CO KG
  • EP3821142B1 patent drawingFigure 1a~2b
  • EP3821142B1 patent drawingFigure 3a~3b

AI summary

In a connection bolt (1) for connecting two parts, more particularly furniture panels, having a cylindrical bolt shaft (2) for anchoring in a borehole of the one part and with a bolt head (3) for anchoring in a borehole of the other part, the bolt head (3) having a foot portion (4) adjoining the bolt shaft (2) and a hook-shaped head portion (5) with a blade-shaped projection (6) that projects radially outwards, the foot portion (4) is arranged with respect to the bolt shaft (2) eccentrically offset in the radial direction (7) in which the projection (6) projects radially outwards.