Contoured Chair Back Assembly With Pre-Stretched Spline Fabric

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Solution Overview

Problem

Conventional office chairs face challenges in securely attaching a suspension fabric to a contoured back frame, which affects the comfort and adjustability of the chair.

Innovation Solution

A method involving a press-fitted elastomeric spline into an annular spline channel around the back frame's periphery, pre-stretching and securing the suspension fabric to maintain a comfortable and adjustable seating arrangement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a suspension fabric is attached to a contoured back frame using conventional methods, then the attachment security is insufficient, but using a spline channel with press-fitted elastomeric spline improves attachment security while allowing complex frame contours

Engineering Contradiction:
Improveattachment securityVSAvoidframe contour complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The back frame is divided into molded front and back ring sections that are assembled together, with each section grooved to define portions of the spline channel. This segmentation allows complex contours to be formed while still permitting spline channel formation about the periphery

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

An elastomeric spline is introduced as an intermediary component that is press-fitted into the spline channel to secure the suspension fabric. This mediator enables reliable attachment while accommodating the contoured shape of the frame

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of operation

If the suspension fabric is pre-stretched during assembly, then the comfort and adjustability are improved, but the manufacturing process complexity increases

Engineering Contradiction:
Improvechair adjustabilityVSAvoidfabric attachment process
Core Design Contradiction:
Ease of operationVSEase of manufacture

Solution Approach 1:

The suspension fabric is pre-stretched during assembly before being secured to the frame by the spline. This preliminary action ensures the fabric is in its stretched condition during attachment, providing immediate comfort and adjustability

Inventive Principle:
Principle #10Preliminary action

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 a secure and comfortable attachment of the suspension fabric to the contoured back frame, enhancing the chair's adjustability and occupant support while allowing for complex frame contours.

Implementation Method 1

The suspension fabric comprises a single layer of suspension material which connects to the frame by a plastic spline that is press fitted into an annular spline channel

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentUS7461442B2Assembly apparatus and process for a chair back
Publication Date: 2008.12.09 HAWORTH INC
  • US7461442B2 patent drawing
  • US7461442B2 patent drawing
  • US7461442B2 patent drawing

AI summary

An office chair is provided having a contoured back assembly comprising a back frame and a suspension fabric. The fabric is attached to the back frame through a spline wherein the back frame has a three-dimensional contoured shape formed by overlapped frame rings with the fabric being joined thereto by a spline. The fabric is secured to the frame by a machine wherein the fabric is first stretched from the outer edge of the fabric and then is clamped to a frame surface in the pre-tensioned or pre-streched condition. The fabric edges are allowed to hang loose and then fixed in the frame by a spline. Once secured, the fabric is unclamped from the frame.