Chair Seat Return Force Mechanism for Posture Changeability

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Solution Overview

Problem

Conventional chairs with integral seats and backrests or synchronized locking mechanisms struggle to return to a reference position when moved forward or backward, limiting posture changeability and comfort during long periods of sitting.

Innovation Solution

A chair with a return force generation mechanism that increases the return force as the seat moves away from the reference position, allowing for forward and backward movement, and featuring separate elastic members for forward and backward movements to adjust the return force based on the direction and amount of movement, ensuring the seat can stop at an appropriate position and assist in posture changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a conventional reaction force mechanism is utilized in a swingable chair, then the chair can move forward and backward, but the chair swings forward or backward from a reference position and the function to return the chair back to the reference position may not be realized

Engineering Contradiction:

Improveposture changeabilityVSAvoidreturn to reference position function

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The return force mechanism is divided into two independent elastic members: a first elastic member for forward movement and a second elastic member for backward movement. Each member is responsible for returning the seat in one specific direction, ensuring reliable return function while maintaining posture changeability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different elastic members are assigned to different movement directions with potentially different elastic forces. The first elastic member provides return force for forward movement while the second elastic member provides return force for backward movement, allowing optimized local characteristics for each direction.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If the seat is made movable forward and backward to enhance efficiency and improve posture, then posture changeable range increases, but the chair may not stop at appropriate positions or return to initial reference position

Engineering Contradiction:

Improveposture changeable rangeVSAvoidposition control

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The elastic members provide dynamic return forces that increase with displacement from the reference position. This creates a natural tendency for the seat to return to or stop at appropriate positions, improving position control while maintaining full movement freedom.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The elastic members act as feedback mechanisms that continuously exert return forces proportional to the displacement from the reference position. This automatic feedback ensures the seat returns to or stops at appropriate positions without requiring active control.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If separate elastic members are provided for forward and backward movements, then the return force can be adjusted based on direction and amount of movement, but the device complexity increases

Engineering Contradiction:

Improveadjustable return forceVSAvoidnumber of elastic members

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Each elastic member serves multiple functions: it provides return force in one direction, acts as a stopper at the reference position, and enables posture changes. This multi-functionality reduces the need for additional components despite having separate elastic members for different directions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The return force mechanism and stopper function are merged into the same elastic members. The elastic members not only provide return forces but also act as stoppers when the seat reaches the reference position, eliminating the need for separate stopper components.

Inventive Principle:

Principle #5Merging (Combining)

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 chair allows for increased posture changeability, reducing fatigue during long sitting periods by enabling the seat to return to a balanced position, providing adjustable return force based on user size and preference, and reducing the number of components while maintaining functionality.

Implementation Method 1

an elastic member configured to increase the return force in the direction to return the seat to the reference position as an amount of movement of the seat from the reference position increases

Methodology Applied

Scientific EffectElastic force: Elasticity

Data Source

PatentUS11253077B2Chair with return force mechanism

Publication Date: 2022.02.22 KOKUYO CO LTD

AI summary

A chair according to the present invention has a reference position P located midway in a front-back direction in a movable range of a seat 2. The chair includes a return force generation mechanism 4 configured to generate a return force in a direction to return the seat 2 moved from the reference position P at least in the front-back direction to the reference position P. The return force generation mechanism 4 includes an elastic member 40 configured to increase the return force in the direction to return the seat to the reference position P as the amount of movement of the seat from the reference position P increases.