Conductive Furniture Caster for Hidden Static Discharge

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Solution Overview

Problem

Existing anti-static casters for furniture are aesthetically unpleasing, unreliable, and prone to breakage or wear due to unsightly conductive wires rubbing on the ground, with uncertain electrical connections between conductive elements and the pivot/rotation shaft, leading to inadequate static electricity discharge.

Innovation Solution

A caster design featuring a conductive wheel with a rotatable pivot and rotation shaft, where the wheel is either integral with the shaft or mounted via ball bearings, with a crimped conductive wire connection and a non-conductive cover, ensuring reliable static discharge without an unsightly conductive tab, using conductive materials for pivot, shaft, and wheels with conductive-doped plastic.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conductive wire is used to discharge static electricity, then static discharge function is achieved, but the wire rubs on the ground causing aesthetic degradation and reliability issues

Engineering Contradiction:
Improvestatic discharge reliabilityVSAvoidaesthetic degradation
Core Design Contradiction:
ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The conductive wire is extracted from the ground-contacting position and relocated to the rotation shaft. The wheel itself is made conductive through doping, so the wire no longer needs to rub on the ground to discharge static electricity. This extracts the harmful ground-rubbing function while preserving the static discharge capability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The electrical conductivity parameter is changed from being localized in a ground-rubbing wire to being distributed throughout the wheel material itself through doping. This parameter change allows the wheel to discharge static electricity without requiring a separate conductive wire to contact the ground.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If a conductive wire is used for static discharge, then static electricity can be discharged, but the wire and connection components are prone to breakage and wear

Engineering Contradiction:
Improvestatic discharge functionVSAvoidcomponent service life
Core Design Contradiction:
ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The conductive wire is extracted from the ground-contacting position and relocated to the rotation shaft. The wheel itself is made conductive through doping, so the wire no longer needs to rub on the ground to discharge static electricity. This extracts the harmful ground-rubbing function while preserving the static discharge capability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The conductive function is merged into the wheel structure itself through doping the plastic material. Instead of having a separate conductive wire that can break or wear, the wheel becomes inherently conductive, eliminating the weak link of the wire and its connections.

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If complex connection means are used to mount the conductive wire to the pivot, then electrical connection can be achieved, but the device complexity increases

Engineering Contradiction:
Improveelectrical connection reliabilityVSAvoidconnection structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The conductive function is merged into the wheel structure itself through doping the plastic material. Instead of having a separate conductive wire that can break or wear, the wheel becomes inherently conductive, eliminating the weak link of the wire and its connections.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The wheel serves multiple functions: it provides mechanical rotation support and simultaneously provides electrical conductivity for static discharge. This multi-functionality eliminates the need for separate conductive components and complex connection structures.

Inventive Principle:
Principle #6Universality (Multi-functionality)

4Reliability

If conductive materials are used for the wheel, then static discharge is improved, but the aesthetic appearance deteriorates due to visible conductive elements

Engineering Contradiction:
Improvestatic discharge effectivenessVSAvoidaesthetic appearance
Core Design Contradiction:
ReliabilityVSShape

Solution Approach 1:

The electrical conductivity parameter is changed from being localized in a ground-rubbing wire to being distributed throughout the wheel material itself through doping. This parameter change allows the wheel to discharge static electricity without requiring a separate conductive wire to contact the ground.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The conductive doping is applied throughout the wheel material rather than using visible conductive wires or tabs. This local quality change allows the entire wheel to be conductive while maintaining a uniform, aesthetically pleasing appearance without exposed conductive elements.

Inventive Principle:
Principle #3Local quality

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 design provides a reliable, aesthetically pleasing, and cost-effective solution for static electricity discharge, ensuring consistent contact and reduced manufacturing costs while maintaining the natural color and light weight of the non-doped plastic cover.

Implementation Method 1

The roller further comprises a set of electrically conductive elements mounted in series, namely: the pivot which is connected to the piece of furniture, the rivet, the electrically conductive wire, the rotation shaft and the wheel

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

indirectly via bearings balls which are generally made of an electrically conductive material, for example metallic, such as steel or the like

Methodology Applied
Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentEP2392229B1Caster for furniture foot
Publication Date: 2012.11.21 TENTE ROULETTES POLYMERES BRUANDET
  • EP2392229B1 patent drawingFigure 1
  • EP2392229B1 patent drawingFigure 2~4

AI summary

The roller has an electrically conductive wire (60) with an end (61) set on an end (58) of a rivet shank (54) of a rivet (52), and another end (62) that is in contact with a rotating shaft (12). The latter end of the wire is housed in a groove (66) realized in a bearing (16). The groove comprises depth equal to thickness of the latter end of the wire. A pivot (40), shaft and a wheel (10) are made of electrically conductive materials. Length of an plug end fitting (42) of the pivot is determined such that an end (49) of the fitting located in a blind hole (30) is in contact with the shank.