Chair Backrest Reaction Mechanism With Lateral Spring Adjustment

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Solution Overview

Problem

Existing reaction force mechanisms for chair backrests are bulky, costly, and difficult to adjust due to the vertical orientation of reaction springs, which limits the use of longer springs and results in a monotonous rocking hardness and inefficient space utilization.

Innovation Solution

A reaction force mechanism with a laterally oriented reaction spring, allowing for the use of longer springs and incorporating a lock mechanism with a stopper member and drive portion to adjust the spring's initial compression and angle, enabling flexible reclining angles and improved usability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the reaction force spring is disposed vertically near the rotation shaft, then the spring can directly receive the swing of the back support member, but the spring protrudes in the vertical direction and takes up space under the seat, causing disfigurement and requiring a large cover

Engineering Contradiction:

Improvereaction force generationVSAvoidspace under the seat

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The reaction force spring is repositioned from a vertical orientation near the rotation shaft to a lateral orientation in the front space under the seat. This dimensional change moves the spring from the constrained back space to the more spacious front area, allowing it to be concealed without requiring a large cover while maintaining its functional effectiveness

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Force

If the reaction force spring is disposed vertically near the rotation shaft, then the spring can generate reaction force, but the spring has to be short and therefore a strong and rigid spring is required, increasing cost

Engineering Contradiction:

Improvereaction forceVSAvoidcost

Core Design Contradiction:

ForceVSEase of manufacture

Solution Approach 1:

By changing the spatial parameters of the spring installation - specifically extending the spring in the lateral direction rather than using a short vertical spring - the system can achieve the required reaction force with a longer, less rigid spring. This parameter change allows the use of cheaper spring materials and reduces manufacturing costs while maintaining the necessary force generation capability

Inventive Principle:

Principle #35Parameter changes

3Force

If the reaction force spring is disposed vertically near the rotation shaft, then the spring can generate reaction force, but the rocking hardness is monotonous and it is difficult to adjust the rocking hardness

Engineering Contradiction:

Improvereaction forceVSAvoidrocking hardness adjustment

Core Design Contradiction:

ForceVSEase of operation

Solution Approach 1:

The invention introduces an adjustable mechanism that allows the initial compression amount and angle of the reaction force spring to be modified. This dynamic adjustment capability enables users to change the rocking hardness according to their preferences, transforming the static spring system into an adaptable one that can provide varied rocking characteristics

Inventive Principle:

Principle #15Dynamics

4Device complexity

If the backrest support structure and reaction force spring mechanism are concentrated on the back space, then the structure is compact, but it causes more bloating in a height direction than necessary and is against slimming down

Engineering Contradiction:

Improvestructural compactnessVSAvoidheight

Core Design Contradiction:

Device complexityVSLength of stationary object

Solution Approach 1:

The reaction force spring mechanism is redistributed from the vertical back space to the lateral front space under the seat. This spatial redistribution maintains structural compactness while eliminating the height bloating effect, allowing the chair to have a slimmer profile without compromising the mechanical functionality

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 reduces costs by using weaker, less expensive springs, enhances space utilization under the seat, and allows for adjustable reclining angles, providing a more comfortable and upscale rocking experience.

Implementation Method 1

a reaction force spring for applying a spring force for returning the back support member to an original position

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a weight-dependent reaction force mechanism for moving the seat support member in a lifting direction in relation to the reclining of the back support member

Methodology Applied

Scientific EffectGravitation: Gravitation

Data Source

PatentUS8998322B2Reaction force mechanism for backrest of chair and chair mounted with the same

Publication Date: 2015.04.07 TAKANO CO LTD

AI summary

Reaction force mechanism for backrest of a chair has clear large space under the seat and uses a longer reaction force spring than the prior art. The mechanism includes a base member supported on a leg, a back support member coupled by a rotation shaft to the base member to recline and support the backrest, a seat support member to which the seat is mounted, a weight-dependent reaction force mechanism for moving the seat support member in a lifting direction, and a reaction force spring for applying a spring force for returning the back support member to an original position, in which the reaction force spring is disposed in a lateral orientation between the back support member and the seat support member.