Multi-Joint Central Unit for Office Chair Recyclability

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Solution Overview

Problem

Conventional office chairs have complex structures that are difficult to recycle due to numerous components, some of which are not recyclable, posing challenges in sustainability and recyclability.

Innovation Solution

A central unit for a chair, comprising a multi-joint body with at least three flexural joints made from a single material, preferably plastic, that can be manufactured through injection molding, allowing easy assembly and disassembly for recycling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional metal mechanical components are used for the central unit, then structural strength and stability are ensured, but recyclability and sustainability are compromised due to complex multi-material construction

Engineering Contradiction:
Improvestructural strengthVSAvoidrecyclability
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The patent merges multiple functional components (seat part, backrest part, support part, and joints) into a single integrated multi-joint body manufactured from one material. This consolidation eliminates the need for separating multiple materials during recycling, directly resolving the contradiction between maintaining structural strength and improving recyclability.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent employs homogeneity by constructing the entire central unit from a single material type, replacing conventional multi-material assemblies. This homogeneous construction maintains sufficient structural strength while enabling straightforward recycling processes, as the entire component can be processed together without material separation.

Inventive Principle:
Principle #33Homogeneity

2Adaptability or versatility

If multiple different joints are provided for assembling the central unit, then functional requirements are met, but device complexity increases and manufacturing becomes more difficult

Engineering Contradiction:
Improvefunctional requirementsVSAvoidnumber of different joints
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements universality by designing all joints with a uniform structure and material composition. Each joint, despite connecting different components (seat to backrest, backrest to support, etc.), shares the same design characteristics, allowing a single joint type to serve multiple functions throughout the central unit, thereby reducing complexity while meeting all functional requirements.

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

Solution Approach 2:

The patent segments the central unit into distinct functional parts (seat part, backrest part, support part, front part) connected by standardized joints. This segmentation allows each joint to be independently designed with a universal configuration, simplifying manufacturing and assembly while maintaining the necessary adaptability for different functional requirements.

Inventive Principle:
Principle #1Segmentation

3Ease of operation

If flexural joints are designed as separate components, then assembly flexibility is improved, but the number of parts increases and recycling becomes more complex

Engineering Contradiction:
Improveassembly flexibilityVSAvoidnumber of parts
Core Design Contradiction:
Ease of operationVSQuantity of substance

Solution Approach 1:

The patent merges the flexural joints with the adjacent rigid parts through material fit, creating an integrated multi-joint body. This combination reduces the total number of separate components while maintaining assembly flexibility, as the flexural joints remain functional within the integrated structure and can be manufactured in one piece using injection molding.

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 solution enables a chair with fewer components that can be easily recycled, reducing waste and aligning with sustainability goals by simplifying the recycling process.

Implementation Method 1

A flexural joint is based on the principle of elasticity. The function of a joint is achieved by an area that has lower flexural rigidity than two adjacent regions.

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP4573969A1Central unit for an office chair
Publication Date: 2025.06.25 INTERSTUHL BUEROMOEBEL GMBH & CO KG
  • EP4573969A1 patent drawingFigure 1~2
  • EP4573969A1 patent drawingFigure 3~4
  • EP4573969A1 patent drawingFigure 5~6

AI summary

The invention relates to a central unit (10, 10a, 10b, 10c, 10d) for a chair, in particular an office chair, characterized by a multi-joint body (12, 12a, 12b, 12c, 12d, 12e, 12f) which has a seat part (14) for a seat (16), a backrest part (18) for a backrest (20), a support part (22) for a support of a base frame and a front part (24, 24a) arranged between the seat part (14) and the support part (22), wherein the multi-joint body (12, 12a, 12b, 12c, 12d, 12e, 12f) has at least three joints (26, 28, 30, 32), which each connect two of the said parts in an articulated manner.