Chair Backrest Locking Mechanism Prevents Deformation

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Solution Overview

Problem

Existing chair backrests suffer from deformation and cracking issues due to backward forces from a human back, primarily because the hinge axis is prone to stress and strain.

Innovation Solution

A chair backrest folding locking mechanism that includes a fixing bracket, a transverse locking member, and resisting parts, which allows the chair backrest to rotate and lock into place, distributing stress and preventing deformation and cracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the hinge axis method is used to connect the chair backrest to the seat cushion bracket, then the chair backrest can be folded for compact storage, but the hinge joint is prone to cracking and the chair backrest undergoes deformation under backward force from a human back

Engineering Contradiction:

Improvefolding capabilityVSAvoidstructural stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The connection structure is divided into multiple functional components: hinge axis for folding, locking member for stabilization, and resisting parts for force distribution. This segmentation allows each component to perform its specific function optimally - the hinge enables folding while the locking and resisting mechanisms prevent deformation under load.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The locking member is pre-positioned to engage with the fixing bracket before the backrest is subjected to backward force. The resisting parts are also pre-installed to provide immediate structural support. This preliminary action ensures that the backrest is stabilized in its vertical position before any deforming force is applied, preventing cracking and deformation.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If the hinge joint is used without additional locking mechanisms, then the structure is simple, but the hinge joint is prone to cracking under stress

Engineering Contradiction:

Improveconnection structureVSAvoidresistance to cracking

Core Design Contradiction:

Device complexityVSStrength

Solution Approach 1:

The locking member acts as an intermediary between the hinge axis and the backrest structure. It mediates the stress by providing an additional anchoring point that distributes the load away from the hinge joint, preventing the hinge from cracking under stress while maintaining structural integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The locking member is pre-positioned to engage with the fixing bracket before the backrest is subjected to backward force. This preliminary action ensures that the backrest is stabilized in its vertical position before any deforming force is applied, preventing cracking and deformation.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the transverse locking member is added to lock the chair backrest, then the resistance to deformation and cracking is improved, but the device complexity increases

Engineering Contradiction:

Improveresistance to deformationVSAvoidlocking mechanism

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The locking member is merged with the existing hinge axis structure, sharing the same mounting location and integrating seamlessly with the folding mechanism. The resisting parts are also integrated into the overall connection assembly. This merging approach adds locking functionality without creating a separate, complex subsystem, thereby minimizing the increase in device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The locking member serves multiple functions: it provides structural support to prevent deformation, acts as a stress distribution point to prevent hinge cracking, and works in conjunction with the resisting parts to stabilize the backrest. This multi-functionality reduces the need for additional separate components, keeping the overall device complexity manageable.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 mechanism effectively prevents deformation and cracking of the chair backrest by locking the transverse locking member into place, ensuring the chair backrest remains stable and secure under external forces.

Implementation Method 1

The driving member is a spring

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS20250194804A1Chair backrest folding locking mechanism and folding chair

Publication Date: 2025.06.19 ZHEJIANG YUEQIANG FURNITURE TECH CO LTD

AI summary

A chair backrest folding locking mechanism is provided, which includes a fixing bracket, defining a locking hole disposed transversely; a chair backrest, hinged with the fixing bracket; a transverse locking member, disposed on the chair backrest, where an outer end of the transverse locking member extends laterally from a lower end of the chair backrest, and the transverse locking member telescopically moves relative to the chair backrest in a transverse direction; a driving member, driving the outer end of the transverse locking member to extend into the locking hole; a front side resisting part, disposed on the fixing bracket and below the chair backrest, and located at a side of the chair backrest proximate to a human back; and a rear side resisting part, disposed on the lower end of the chair backrest. Therefore, the chair backrest can be folded and unfolded, and make the chair backrest stable under stress.