Chair Backrest Crossbar Structure for Ergonomic Flex and Assembly
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Solution Overview
Problem
Existing chair backrests do not provide adequate ergonomic support and are difficult to assemble, making them costly and limiting the option for interchangeable armrests.
Innovation Solution
A backrest design featuring an elastically deformable crossbar with adjustable lumbar support and a reinforced back cover, allowing for synchronized movement with the seat, and easy attachment of different armrests through a mechanism that includes a latching system and adjustable components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the crossbar is made rigid to support user weight, then structural strength is improved, but ergonomic adaptability deteriorates
Solution Approach 1:
The crossbar is designed with elastic deformability, allowing it to dynamically adapt its shape under user weight while maintaining structural integrity. The height being a multiple of thickness enables controlled elastic deformation that provides ergonomic adaptation without compromising strength.
Solution Approach 2:
The crossbar's geometric parameter (height as multiple of thickness) is specifically designed to achieve optimal balance between rigidity and elastic deformability, allowing it to withstand user weight while adapting ergonomically through controlled deformation.
2Reliability
If the backrest uses a complex assembly structure to improve ergonomic support, then ergonomic support is improved, but assembly ease deteriorates
Solution Approach 1:
The backrest is divided into modular components (side arms, crossbar, lumbar support, back cover) that can be independently manufactured and assembled. The connection elements with latching mechanisms enable simple snap-fit assembly without complex fastening operations.
Solution Approach 2:
The latching connection system enables self-aligning and self-securing assembly, where the connection elements automatically engage with complementary organs on the crossbar, eliminating the need for precise manual alignment or additional fastening steps.
3Ease of operation
If the backrest frame is made as a single integrated piece to simplify assembly, then assembly ease is improved, but adaptability for interchangeable armrests deteriorates
Solution Approach 1:
The backrest frame is segmented into side arms with integrated connection elements, creating natural attachment points for armrests. This modular structure allows different armrest configurations while maintaining simple assembly through the latching system.
Solution Approach 2:
The connection elements on the side arms serve multiple functions: structurally supporting the crossbar and providing standardized attachment points for various armrest types, enabling versatility without complicating the basic assembly process.
4Quantity of substance
If the back cover is made thin to reduce material usage, then material cost is reduced, but structural strength deteriorates
Solution Approach 1:
The back cover is designed with varying thickness or reinforcement at critical locations (such as attachment areas and load-bearing zones) while maintaining thinner sections in non-critical areas, optimizing the balance between material usage and structural strength.
Solution Approach 2:
The back cover may utilize composite material structures or reinforcement strategies that provide enhanced strength-to-weight ratio, allowing thin construction while maintaining adequate structural performance for ergonomic support.
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
Enhances ergonomic support by adapting to user weight, providing comfortable curvature and allowing for easy assembly and interchangeable armrests, improving user experience and reducing assembly costs.
Implementation Method 1
the cross bar is elastically deformable under load from a user sitting in the chair in the direction of the force exerted by the leaning user's back
Implementation Method 2
The upper ends of the side arms have connection elements which interact in a latching manner with complementary organs on the crossbar
Data Source
Figure 1A~1B
Figure 2~3A
Figure 3B~3C
AI summary
The chair, for which the backrest (4) is designed, has an underframe (1) sitting on the ground, a mechanism (2) placed onto the underframe (1), and a seat (3) placed onto the mechanism (2). The backrest (4) is fastened to the mechanism (2), wherein the backrest (4) comprises a backrest frame (40), over the inside surface of which a backrest cover (8) is stretched. The backrest frame (40) has a lower base section (42), from which a lateral arm (43) extends upward on either side, wherein the upper ends of the lateral arms are bridged by a cross bar (44), which elastically deforms under the load of a user sitting in the chair in the direction of the force applied by the back of the user resting thereon, but is flexurally rigid against the action of the force perpendicularly from above. The height of the cross bar (44) is multiple times that of the thickness in the cross-section. The backrest cover (8) is provided with seams (80) strengthening the backrest cover (8) over a bordered free space between the base section (42), the lateral arms (43) and the cross bar (44).