Chair with plastic frame and cantilevered arm rest
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Solution Overview
Problem
Existing chairs lack stability when stacked, have high dead weight, and high assembly costs, making them inefficient for storage and use.
Innovation Solution
A stackable chair design featuring a one-piece plastic frame with solid chair legs and armrest supports, where the armrests are free-swinging and supported only by armrest supports, and the frame is detachably connected to a seat shell, using fiber-reinforced plastic with optional fabric inserts for reinforcement in high-stress areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional chair designs are used, then assembly is straightforward, but stacking stability is poor and dead weight is high
Solution Approach 1:
The frame is made from fiber-reinforced plastic composite material, which provides high strength-to-weight ratio. The plastic material with fiber reinforcement (at least 30 percent by volume) achieves both lightweight construction and sufficient mechanical strength for stable stacking, resolving the contradiction between reducing dead weight and maintaining stacking stability.
Solution Approach 2:
The armrest is divided into separate functional parts: the armrest support integrated with the chair leg and the free-swinging armrest element. This segmentation allows the frame to maintain structural integrity for stacking while reducing overall weight through optimized material distribution.
2Reliability
If complex frame structures are used to improve stability, then stacking stability improves, but manufacturing complexity and assembly costs increase
Solution Approach 1:
Multiple frame components are merged into a one-piece plastic frame manufactured in a single molding process. The chair legs, armrest supports, and connecting elements are integrated into one monolithic structure, eliminating the need for complex assembly operations and reducing manufacturing costs while maintaining structural stability.
Solution Approach 2:
The chair leg serves multiple functions: it provides structural support, forms the armrest support integration point, and creates the stacking interface. This multi-functionality reduces the number of separate components needed, simplifying both manufacturing and assembly processes.
3Strength
If heavy materials are used to reduce dead weight, then structural integrity improves, but the chair becomes harder to move and stack
Solution Approach 1:
Fiber-reinforced plastic provides high specific strength (strength-to-weight ratio). The plastic matrix combined with fiber reinforcement achieves structural integrity comparable to heavier materials while maintaining low dead weight, enabling easy movement and stacking.
Solution Approach 2:
The cross-sectional geometry of the chair legs is optimized with closed sections and specific dimensional ratios. The circumference-to-area ratio is controlled to provide sufficient structural strength while minimizing material usage and overall weight.
Data Source
Figure 1~2
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AI summary
The invention relates to a chair with a seat (3), a backrest (4), two front (21) and two rear chair legs (31), and two armrests (50), wherein the seat (3) and the backrest (4) form a single-piece seat shell (2). The chair legs (21, 31) and the freely suspended armrests (50) form a single-piece frame (20) made of plastic. Each armrest (50) consists of an armrest support (52) and an armrest pad (60). The armrest supports (52) lie in the same plane as the front chair legs (21, 31). The frame (20) and the seat shell (2) are detachably connected to each other. The present invention provides a chair that is stackable while offering secure stability, low weight, and easy assembly.