Chair Mechanical Assembly With Adjustable Leaf Springs for Body Weight Tuning

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Solution Overview

Problem

Existing chair mechanical assemblies lack precise adjustment to accommodate varying body weights, leading to inadequate support and comfort, particularly for individuals within specific weight classes.

Innovation Solution

A mechanical assembly for a chair featuring a one-piece seat shell connected via elastic elements, with adjustable leaf springs and supports that adjust based on body weight, ensuring optimal support and comfort through a system of leaf springs, adjustable supports, and a mechanism that compensates for body weight by altering the position and restoring force of the seat shell.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If fixed leaf springs are used to compensate for body weight, then the basic support function is provided, but the adjustment precision for different body weights is insufficient

Engineering Contradiction:
Improveadjustment precision for body weightVSAvoidmechanical assembly complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies dynamics by making the leaf spring system adjustable rather than fixed. The supports can be repositioned along the leaf springs, and the leaf springs themselves can be exchanged for different stiffness values. This dynamic adjustability allows precise tuning for different body weights while maintaining a relatively simple mechanical structure.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent implements parameter changes by allowing variation in the stiffness parameter of the leaf springs through exchanging different leaf springs with varying stiffness values. It also allows changing the position parameter of the supports along the leaf springs. These parameter adjustments enable precise compensation for different body weights without significantly increasing device complexity.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If the seat shell is connected indirectly through the mechanical assembly, then the mechanical assembly can provide support and adjustment, but the connection stability and support consistency are reduced

Engineering Contradiction:
Improveconnection stabilityVSAvoidmechanical assembly structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the seat shell into separate components (seat element and back element) connected by elastic elements. This segmentation allows the mechanical assembly to provide controlled support and adjustment while maintaining connection stability through the elastic coupling between segments.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent uses elastic connection elements as intermediaries between the seat element and back element. These elastic elements mediate the connection, providing both stability and flexibility, allowing the mechanical assembly to adjust support characteristics while maintaining reliable connection between seat shell components.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Ease of operation

If adjustable supports are introduced to improve body weight compensation, then the tuning precision is improved, but the device complexity increases

Engineering Contradiction:
Improvetuning ease for body weightVSAvoidadjustment mechanism complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The patent makes the support system dynamic by allowing the supports to be repositioned along the leaf springs. This dynamic adjustment capability improves ease of operation for tuning to different body weights while keeping the adjustment mechanism relatively simple - primarily involving movable supports that can be repositioned rather than complex mechanical systems.

Inventive Principle:
Principle #15Dynamics

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 provides improved comfort and support by allowing finer tuning to individual body weights, ensuring consistent and adequate support across a range of users, particularly those weighing between 40 kg to 60 kg, through precise adjustment of the seat shell's position and restoring force.

Implementation Method 1

the mechanism assembly comprises at least one leaf spring to compensate for a body weight of a seated person

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

the seat element is connected to the back element by a connecting means such as in particular at least one connecting joint or at least one elastic connection element

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP3270733B1Mechanical assembly for a chair and chair with such a mechanical assembly
Publication Date: 2019.05.08 HERMAN MILLER INC
  • EP3270733B1 patent drawingFigure 1
  • EP3270733B1 patent drawingFigure 2
  • EP3270733B1 patent drawingFigure 3

AI summary

The invention relates to a mechanical assembly (2), said mechanical assembly (2) comprising, in addition to a leaf spring, at least one further spring element, the elastic restoring force of the at least one further spring element and the elastic restoring force of the one or more leaf springs supporting the seat shell (S) with a total restoring force, and/or the mechanical assembly (2) comprising at least two leaf springs and at least two supports, each support being associated with one of the leaf springs, and at least two supports being displaceable beneath the leaf springs by means of an adjustment mechanism and being displaceable on their trajectories by different extents.