Chair with Adjustable S-Shaped Leaf Spring for Dynamic Sitting

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Solution Overview

Problem

Existing chair designs lack adjustability in swivel movement, particularly in adapting to different user weights and preferences, limiting the dynamic sitting experience.

Innovation Solution

A chair design featuring an S-shaped leaf spring with a compressible spacer adjustable along its first section, allowing adjustment of the effective lever arm and spring firmness, facilitated by a mechanism that changes the spring force through a rotating actuating element.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a fixed synchronous mechanism is used to couple the backrest and seat, then the movement ratio is stable, but the adjustability for different user weights and preferences is limited

Engineering Contradiction:
ImproveadjustabilityVSAvoidmechanism complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies the dynamics principle by making the synchronous mechanism adjustable rather than fixed. The lever arm length can be dynamically changed to adapt to different user weights and preferences, transforming a static mechanism into a dynamic one that can be customized for different users while maintaining operational stability

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent implements parameter changes by allowing modification of the lever arm length parameter in the synchronous mechanism. This enables adjustment of the movement characteristics to suit different users, achieving adaptability through changing a key geometric parameter without fundamentally altering the mechanism structure

Inventive Principle:
Principle #35Parameter changes

2Strength

If the spring element is made stiffer to support heavier users, then load-bearing capacity increases, but comfort for lighter users decreases

Engineering Contradiction:
Improveload-bearing capacityVSAvoidcomfort adaptability
Core Design Contradiction:
StrengthVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by enabling the spring system's effective stiffness to be adjusted based on user needs. Through changing the lever arm length, the same spring element can provide appropriate support for both lighter and heavier users, achieving adaptability without requiring multiple different spring elements

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent implements universality by designing a single spring element that can serve multiple user weight categories through adjustment of the lever arm length. This allows one spring system to universally accommodate different users by changing its mechanical advantage rather than requiring separate spring elements for different weight classes

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

3Adaptability or versatility

If multiple spring elements are used to provide adjustment ranges, then adaptability improves, but the number of components and device complexity increases

Engineering Contradiction:
Improveadjustment rangeVSAvoidnumber of components
Core Design Contradiction:
Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent applies segmentation by dividing the adjustment function into two independent aspects: spring element selection (for basic stiffness levels) and lever arm length adjustment (for fine-tuning). This segmentation allows achieving comprehensive adjustability without proportionally increasing the total number of components, as the lever arm adjustment provides continuous variability without requiring additional spring elements

Inventive Principle:
Principle #1Segmentation

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

Enables three-dimensional dynamic sitting by allowing adjustable reclining and lateral movements, accommodating various user weights and preferences with enhanced comfort and reduced component count.

Implementation Method 1

at least one S-shaped leaf spring (4), wherein the S-shaped leaf spring (4) is deflectable with respect to both bending and twisting

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

A compressible spacer (6) is provided between the first and second sections (4a, 4b) and is adjustable in the longitudinal direction of the first section (4a)

Methodology Applied
Scientific EffectCompression: Compression

Data Source

PatentEP4702877A1Chair
Publication Date: 2026.03.04 WILKHAHN WILKENING HAHNE GMBH & CO
  • EP4702877A1 patent drawingFigure 1~2
  • EP4702877A1 patent drawingFigure 3~4
  • EP4702877A1 patent drawingFigure 5~6

AI summary

The chair according to the invention comprises a seat (1), a backrest (2), a support frame (3), and at least one S-shaped leaf spring (4), wherein the S-shaped leaf spring (4) is attached to the support frame (3) by a first section (4a), the seat (1) is held by a second section (4b), and the backrest (2) is held by a third section (4c), wherein a first curvature (4d) is provided between the first (4a) and the second section (4b) such that, in a rest position of the chair, the first section (4a) and the second section (4b) are arranged substantially parallel to each other and spaced apart, and the third section (4c) connects to the second section (4b) via an opposing second curvature (4e). A compressible spacer (6) is provided between the first (4a) and the second section (4b), which is adjustable in the longitudinal direction of the first section (4a).