Chair Foot Ring Bush Structure for Stable Height Clamping

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Solution Overview

Problem

Conventional foot ring fixing structures for chairs suffer from uneven force distribution and reduced clamping force due to the design of the clamping ring, leading to discomfort and instability in adjusting the height position.

Innovation Solution

A fixing structure featuring a bush with a tapered outer surface and internal threads, a shaft hole with a groove and pads, allowing for easy assembly and adjustment of the foot ring's height by rotating the bush to clamp or release the supporting post, utilizing a flange and angled sidewalls for secure engagement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a straight-shape pressing sheet is used in the clamping ring, then the structure is simple, but the force distribution is uneven and clamping force is reduced

Engineering Contradiction:

Improvestructure simplicityVSAvoidclamping force

Core Design Contradiction:

Device complexityVSForce

Solution Approach 1:

The pressing sheet is changed from a straight shape to an arc shape that matches the curvature of the clamping ring's inner surface. This curved design allows the pressing sheet to contact multiple points along the arc, distributing the force evenly and maximizing the clamping force on the supporting post while maintaining structural simplicity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Stability of the object's composition

If the foot ring height is fixed, then the structure is stable, but the adaptability to different user needs is reduced

Engineering Contradiction:

Improvestructural stabilityVSAvoidheight adjustability

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The foot ring assembly incorporates a clamping ring with a clamping mechanism that allows the height position to be dynamically adjusted along the supporting post. The user can loosen the clamping mechanism to move the foot ring to a desired height, then tighten it to fix the position, providing adaptability while maintaining stability during use.

Inventive Principle:

Principle #15Dynamics

3Force

If the bush inner diameter is reduced to clamp the supporting post, then the clamping force is improved, but the ease of assembly is reduced

Engineering Contradiction:

Improveclamping forceVSAvoidease of assembly

Core Design Contradiction:

ForceVSEase of operation

Solution Approach 1:

The bush is designed with a tapered outer surface that transitions from a larger diameter at the entrance to a smaller diameter at the clamping end. This gradual parameter change allows easy insertion of the supporting post, while rotation of the bush engages the taper to reduce the effective inner diameter and create strong clamping force.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The tapered bush acts as an intermediary element between the supporting post and the clamping mechanism. The taper geometry mediates the transformation from easy insertion to strong clamping, allowing the post to pass through freely initially, then be securely gripped through rotational engagement of the taper.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 provides a simple, stable, and easy-to-assemble mechanism for adjusting the foot ring's height, ensuring a secure fit and comfortable positioning by distributing force evenly, enhancing user experience.

Implementation Method 1

at least one pad provided on an inner surface of the shaft hole, which is softer relative to the inner surface of the shaft hole and has a relatively high coefficient of friction

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

a bush being a cylindrical body having a tapered outer surface... when the bush rotates toward a first direction, the wall of the bush is restricted by the central hole and the inner diameter of the shaft hole is reduced to clamp and fix the supporting post

Methodology Applied

Scientific EffectTapered geometry mechanical advantage: Mechanical Advantage

Data Source

PatentUS20210259424A1Fixing Structure for a Foot Ring of a Chair

Publication Date: 2021.08.26 FUSCO INDAL CORP

AI summary

A fixing structure for a foot ring of a chair includes the foot ring having a hub with a central hole formed with internal threads on an inner surface thereof; and a bush being a cylindrical body having a tapered outer surface with external threads formed thereon. The bush has a shaft hole penetrating along a longitudinal axis of the bush, a groove penetrating through a wall of the bush, and at least one pad provided on an inner surface of the shaft hole of the bush. The bush is assembled with the hub by screwing the external threads of the bush with the internal threads of the hub. A supporting post penetrates through the shaft hole of the bush. When the bush rotates toward a first direction, the shaft hole is reduced to clamp and fix the supporting post, and when the bush rotates toward a second direction, the shaft hole is enlarged to release the clamping and fixing of the supporting post.