Hollow Chair Shell Reinforcement for Seat-Back Junction Stress
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Solution Overview
Problem
Molded chair designs without external frames are prone to material failure at the seat-back junction due to concentrated stress and strain, leading to inadequate support and potential breakage over time.
Innovation Solution
A one-piece molded chair shell with a hollow, integral support member between the seat and back portions, featuring a cavity formed by cavity walls that distribute stress and provide reinforcement, reducing material failure and increasing lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a molded chair shell without external frame is used, then device complexity is reduced, but strength and reliability deteriorate due to concentrated stress at the seat-back junction
Solution Approach 1:
The chair shell is segmented into functional zones with a distinct hollow support member integrated into the junction area, separating the load-bearing function from the shell structure while maintaining visual simplicity and reducing overall structural complexity
Solution Approach 2:
The junction area combines the shell material with an integrated hollow support structure formed during molding, creating a composite reinforcement that increases strength without adding separate components or external frames
2Ease of manufacture
If a molded chair shell without external frame is used, then ease of manufacture is improved, but reliability deteriorates due to material failure at the junction area
Solution Approach 1:
The hollow support member is merged with the chair shell into a single integrated component formed during the molding process, eliminating the need for separate reinforcement parts while preventing material failure at the junction area
Solution Approach 2:
The hollow support structure is built into the chair shell during the initial molding process, providing pre-reinforcement at the stress concentration area before the chair is put into service, thereby preventing future material failure
3Strength
If reinforcement is added to the chair shell, then strength is improved, but device complexity increases
Solution Approach 1:
The reinforcement structure is merged with the chair shell into a single integrated component, providing strength enhancement without adding separate parts or increasing overall structural complexity
Solution Approach 2:
The hollow support member changes the local structural parameters at the junction area by creating a reinforced geometry with improved stress distribution, achieving higher strength without complex additional components
Data Source
AI summary
A molded chair shell includes a seat portion and a back portion joined at a junction area. A support or reinforcement member is located at the junction area and is formed integrally with the seat portion and the back portion. The reinforcement member includes an internal cavity between the seat portion and the back portion that is substantially positioned over the junction area. The cavity is formed by cavity walls, which may form ribs that extend forwardly along the seat portion and upwardly the back portion of the chair shell. The chair shell may be formed in an injection molding process, and the internal cavity may be formed in a gas assist operation carried out during the injection molding process.